physical therapy approaches for strengthening the stiffle

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Proceedings of the 57th Annual Convention of

the American Association of Equine Practitioners

- AAEP -

November 18-22, 2011 San Antonio, Texas, USA

Next Meeting : Dec. 1-5, 2012 - Anaheim, CA, USA

www.ivis.org Reprinted in the IVIS website with the permission of the AAEP

Physical Therapy Approaches for Strengtheningthe Stifle and Pelvic Limb

Jennifer H. Brooks, PT, MEd

The physical therapy approach to stifle dysfunction and hindlimb weakness involves client education,increase in the activity level of the horse, and a stretching program followed by a specific ascendingtherapeutic strengthening exercise progression. A thorough examination by a veterinarian shouldfirst clear the horse for physical therapy treatment before initiation of this program. Horsesrecovering from lameness, surgery, or systemic diseases are appropriate for this program. Thecomplementary use of modalities can be beneficial to this exercise program to decrease pain andinflammation and promote healing of tissues. Numerous training aids and therapeutic devices cancontribute to this exercise program progression. This program is intensive for the owner and horsein terms of time and energy for successful outcomes. After the horse is symptom free, a cross-training maintenance program should be used to prevent recurrence. Author’s address: EquineRehabilitation Services, LLC, 23 Dupaw-Gould Road, Brookline, NH 03033; e-mail: [email protected]. © 2011 AAEP.

1. Introduction

Background and Literature Review

The stifle is the largest, most complex joint in thehorse, and it can be, problematically, the weakestjoint.1 Anatomically, this joint corresponds tothe knee joint in humans. Injury specific to thestifle or any structures involving the pelvic limbcan result in proximal muscle disuse atrophy, thuscontributing to stifle pathomechanics and result-ing in impaired limb function. In physical ther-apy treatment of the human knee, the musclessurrounding the knee play pivotal roles specific tostrength, flexibility, structural alignment, andbiomechanical integrity of the patella-femoral andtibio-femoral joints for proper knee function.This role is also true regarding the stifle of thehorse.

Results can be devastating for the stifle joint whenmuscles of the pelvic limb decline in strength sec-ondary to limb injury, surgery, lack of activity, orgrowth spurts. This scenario leads to stifle patho-mechanics, contributing to a malady known as up-ward fixation of the patella (UFP), where the patellabecomes lodged on the medial aspect of the femoralcondyle, resulting in pain, swelling, and inability oflimb flexion and forward locomotion. The horsecannot voluntarily relieve this fixation. The failurein disengagement of the patella is caused by a fail-ure of the quadriceps muscle group to adequatelypull the patella up and off the medial trochlear ridgeof the femur.2 More commonly, in milder cases,there is a partial or intermittent catching of thepatella that results from a delayed release of thepatella, known as intermittent upward fixation ofpatella (IUFP).

158 2011 � Vol. 57 � AAEP PROCEEDINGS

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NOTES

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Proceedings of the AAEP Annual Convention, San Antonio, TX, USA - November 18 - 22, 2011

Several theories postulate that this problem orig-inates from ligaments being too tight or the opposite(being too lax). Research does not substantiate ei-ther of these hypotheses well. Many treatmentsare based on one or the other condition of restrictionor laxity. Various invasive surgical procedures anda multitude of suggestions for conditioning exercisehave had less than favorable results.3 Until therecent decade, not much has been offered to theequine in the way of standard physical therapy orrehabilitation for the treatment of UFP or IUFP.3

Many factors contribute to UFP/IUFP, such as con-formation faults, less than adequate stifle joint an-gulation, youth, and pregnancy, which may not beeasily corrected. Current veterinarian interven-tion for treatment of UFP/ IUFP consists of medialpatellar ligament desmotomy (MPLD),4 medial pa-tellar ligament splitting,5 injection of causticagents,6 estrogen therapy,2 corrective trimming orshoeing (CTS),7 and periods of rest with non-steri-odal anti-inflammatory drugs (NSAIDs)8 along withvague suggestions of exercise conditioning.

Historically, some trainers and veterinarianshave instructed clients to “run him up hills and instraight lines” without specific guidelines. Manystatements similar to these statements are typicalin terms of an exercise protocol when seeking meth-ods to address stifle dysfunction. This statement iscommon in most current sources when referring toconditioning of stifle weakness and rehabilitation.2

A systematic literature review did not reveal anydetailed programs to address stifle dysfunction.Asking a horse presenting with stifle pain andhindlimb weakness to perform hills is most likely toresult in more pain, inflammation, lameness, andpoor performance.

In the human, excessive compressive force or re-petitive use stress may contribute to patellofemoraldegeneration and pathologies, such as patella chon-dromalacia and osteoarthritis.9 Patellofemoralcompressive forces, tibiofemoral compressive forces,and tibiofemoral shear forces all progressively in-crease as the knee flexes and decrease as the kneeextends, reaching peak compressive forces nearmaximum knee flexion.9 Muscle activity generallyprogressively increases as the knees flex and de-creases as the knees extend, which supports athletesperforming the parallel squat (0–90°) over the one-half squat (0–50°).9 Tibiofemoral compressiveforces can equal up to four times one’s bodyweight.10 This force occurs at walking gait and 55°of knee flexion. The patellofemoral joint can en-counter loads as high as 5.1 times the body weight inmidrange flexed positions.10 Therefore, the task ofwalking up stairs or hills, requiring up to 80–90°flexion, could involve joint compressive forces ap-proximately 4–5 times one’s body weight. An in-jured knee with joint effusion, pain, and irritation tounderlying articular cartilage with surroundingmuscle weakness would have difficulty at carryingout such a demanding task in the acute or subacute

stages of recovery. This therapy would be terms formalpractice if a physical therapist (PT) made a hu-man post-surgical knee patient do this regimen inthe acute phase of recovery. Therefore, patientspresenting with these symptoms benefit from amuch less aggressive protocol of pain reduction mo-dalities and muscle toning isometric exercise inavoidance of pain provocation before asking them toperform activities that require knee flexion andstrength, such as hill or stair climbing.

Miller and Swanson2 state, referring to theequine, that “altering the conditioning program canbe helpful to gain adequate quadriceps function.The conditioning should include long, extended,straight exercises. Uphill work with limited down-hill work in good footing is encouraged, but deep soilshould be avoided no matter the type of exercise.Work that involves slow tight circles should beavoided.”2 Jeffcott and Kold8 contribute that“treatment in most of these chronic stifle injuriesconsisted of a period of rest followed by a gradualreturn to exercise; in some cases this was combinedwith a short course of a non-steroidal anti-inflam-matory drug,” but they do not comment on a specificoutline of suggested conditioning exercises.8 Thereare several specific conditioning programs in theliterature aimed at dressage horses11 and thosehorses recovering from tendon12 and ligamentousinjuries13 but not many specific to stifle and pelviclimb weakness post-injury. Denoix and Pailloux14

gave this statement regarding physiotherapy reed-ucation of femorpatellar syndrome: “Go out forwalks, interspersed with trotting: limit on twotracks as well as figures, which involve raising thelegs. Jumps regulated by caveletties, preferable atthe trot.” These examples are non-specific exerciseprogressions with multiple variables in terms ofconditioning.

The most common statement of “work him instraight lines and up hills” is vague, leaving manyquestions for owners and trainers to ponder such ashow much, how often, how does one go only instraight lines when confined to ring work, and howdoes one go uphill and not downhill? What level ofincline is enough or too much? If the horse getssore, how should one proceed: push through orhold off? These are all appropriate questions thathave gone unanswered. Many horses and theirowners have had to proceed through trial and errorbecause of lack of an existing protocol specific forstrengthening the hind end after injury, surgery, orother.

The next few paragraphs will review proposedveterinary treatments for IUFP. Transection ofmedial patellar ligament has historically been rec-ommended, but it is now more commonly reservedfor cases unresponsive to all other treatments andused as a last resort.2 MPLD has been purported toresult in pathologic changes in the articular carti-lage of the patella and adjacent soft tissues.4 Avariety of undesirable conditions that can result

AAEP PROCEEDINGS � Vol. 57 � 2011 159




from MPLD were reported by Gibson and McIl-wraith,4 such as fragmentation formation at the dis-tal aspect of the patella, bone production at theattachment of the middle patellar ligament on thepatella, and articular cartilage fibrillation or detach-ment. Transection of the MPL results in patellarinstability. Without tension from the medial patel-lar ligament, the patella becomes unstable withinthe femoropatellar joint, and femoropatellar synovi-tis and frequently, osteoarthritis result.4 Baccarinet al.15 report an increase in the angle between theproximal articular surface of the patella and thecranial distal surface of the femur along with en-thesophyte formation and lateral deviation of thepatella determined by radiographs after MPLD, con-cluding that MPLD leads to patellar instability.Baccarin et al.15 state that 120 days rest did notprevent the lesions caused by post-surgical patellarinstability. Therefore, the use of this surgical pro-cedure should be reserved for the most persistentcases of upward fixation of the patella.4

Although the mechanism of action is unknown, itis postulated that systemic estrogen relaxes theperipelvic muscles and ligaments, thus altering theangle of the pelvis.4 The alteration in pelvic anglemay decrease the stifle joint angulation and thus,enables the patella to release from the femur.2

Miller and Swanson2 stress the use of exercise inconjunction with estrogen therapy, but they do notspecify what is meant by exercise. Many authorsstate that this approach may be appropriately usedshort term in the young growing horse or pony, butresults are not longstanding.

The use of caustic agents injected into the MPLhas been well-researched.6 The use of injecting 2%iodine in almond oil (IAO) and ethanolamine oleate(EO) are two common agents.6 Histological re-sponses of these agents are thought to cause thick-ening of the MPL through inflammatory response,fibroplasia, and chondroid metaplasia. Injection ofthe patellar ligaments with IAO resulted in agreater increase in cross-sectional area on ultra-sonography than EO. Both agents resulted in sig-nificantly greater fibroplasia relative to controlspecimens.6 It is thought that the mechanism ofirritation, through internal blistering to the liga-ment, will cause the ligament to thicken with scartissue to reduce hyperlaxity. The downside to thisapproach is that if agents are poorly administeredinto the surrounding tissues or joint synovium, im-pending degenerative changes can be catastrophic tothe stifle joint.

MPL splitting has shown the most successful long-term results over other surgical approaches. Tni-bar5 states that the rationale for this surgicalprocedure is to induce localized desmitis with sub-sequent ligament thickening. No short- or long-term complications were observed, and no patientshad clinical signs of UFP after surgery. This clin-ical effect was attributed to a two- to three-foldincrease in size of the proximal part of the MPL from

an induced localized desmitis, concluding that split-ting of the proximal one-third of the MPL is effectivefor treatment of UFP and allows rapid return tonormal activity.5

Other conservative approaches to treatment ofIUFP are evaluation and corrective trimming and/orshoeing (CTS), such as those approaches that Du-moulin et al.7 present in a 2007 retrospective study.Findings indicated that CTS seemed the most im-portant aspect; only 51.6% of patients were success-ful, and 20.3% of them improved partially.7 In caseof no response to conservative treatment or in case ofa permanent fixation, medial patellar desmotomy(MPD) was performed in 20 horses, which correctedUFP completely in 17 of 18 followed-up patients.However, gait abnormalities were seen in 7 of those17 horses post-surgically, but the incidence waslower in horses that had rested for at least 3 mo(25%) compared with horses that had only rested forless than 1 mo (66.6%). Results indicate that con-servative treatment, with special attention for CTS,is worth trying before performing more radical pro-cedures to correct UFP and that a longer convales-cence period after MPLD is desirable.7

Clinical Significance

The clinical significance of stifle dysfunction regard-ing these conditions of UFP and IUFP should not beoverlooked. Repeated trauma to the underlying ar-ticular cartilage of the retro-patella surface can pre-dispose the femoropatellar joint to development ofchondromalacia, a predecessor to osteoarthritis, anddownward decline in function of the equine. It ispossible that this disease is underreported in theliterature because of the difficulty in accurately di-agnosing the condition.16 McLellan et al.16 re-ported that radiography failed to showchondromalacia pathology, nuclear scintigraphy lo-calized the disease process to the femoropatellarregion, and ultrasonography identified pathologicalchanges within the affected joint.16 Repeatedtrauma to the fibro-cartilaginous attachment of theMPL on the patella causes additional tissue prolif-eration, thus causing more surface area to becomehung up on the medial femoral condyle along withadditional irritation that causes local inflammationand a pain cycle.16 Horses with this ongoing con-dition exhibit significant lameness and thus, areoften put in box stalls to rest, which often contrib-utes to additional proximal muscle atrophy of thehindlimb.

All of these previous approaches, with the excep-tion of rest and corrective trimming, are invasiveprocedures, therefore inducing surgical pain, in-flammation, and temporary disability with the pos-sibility of infection and low percentages of provenrecovery. The purpose of this article is to introducephysical therapy approaches to address the problemof stifle dysfunction of delayed patellar release andpelvic limb weakness that are based on approachesused in human knee treatment. Initially, it is im-





portant to minimize pain and inflammation withmodality use as needed and then slowly progresstherapeutic exercise as tolerated to restore properbiomechanics, promoting return to pain-free func-tional locomotion and strength.

This paper will address five objectives:

1. Compare and contrast equine stifle dysfunc-tion to human knee dysfunction known aspatella femoral pain syndrome (PFPS).

2. Determine assessment findings indicative ofUFP/IUFP that are, therefore, appropriatefor this treatment approach.

3. Introduce appropriate use of modalities topromote healing and decrease pain and in-flammation along with training devices andtherapeutic products.

4. Provide a systematic progressive exerciseprotocol of instruction of proper stretchingmethods of shorted structures followed by aprogressive strengthening program initiatedby pain-free isometric contractions and aconcentric work progression to controlled ec-centric contractions.

5. Present the concept of cross-training protocolfor prevention of recurrence.

2. Protocol Development

The development of the following therapeutic exer-cise protocol for treatment of stifle dysfunction (ad-dressing UFP and IUFP symptoms) is based onphysical therapy approaches commonly used to treata similar condition in the human population calledPFPS. PFPS affects approximately one in four peo-ple.17 Human patellofemoral biomechanics differfrom the equine in that patella tends to misalignover the lateral femoral condyle, causing irritationto the retropatellar articular cartilage, and it cansometimes dislocate lateral to the knee joint. Thisbiomechanical fault has been related to poor musclestrength and length, soft-tissue restrictions, youth,pregnancy, deconditioning, and poor skeletalalignment.

Cleland and McRae17 purport that biomechanicaldysfunction of the patellofemoral joint leads to an-terior knee pain and decreased function. The prob-lems of PFPS result from weakened quadriceps,allowing the patella to glide laterally over lateralfemoral condyle and causing roughening of theretro-patellar articular cartilage, which leads to in-flammation and pain; this problem inhibits quadri-ceps function and thus, overall lower limbperformance. Current rehabilitation of PFPS fo-cuses on restoring normal patellofemoral mechanicsby resolving patellofemoral malalignment, promot-ing tissue extensibility, promoting optimal timingand strength of the vastus medialis obliquus mus-cle, and normalizing mechanics.17 Cleland andMcRae17 suggest that the following factors contrib-ute to the cyclic decline of function with equine stifledysfunction: poor biomechanics for the patellar-

femoral joint secondary to delayed neuromotor re-sponse and reflexes of the extensor mechanism ofquadriceps, reduced muscle strength, soft-tissue re-strictions, resulting in poor joint proprioception andfaulty movement.

In both the human and the horse, it is postulatedthat these scenarios are downward, ongoing cyclesthat promote the degradation of the articular carti-lage with decreased joint and limb function. Theprocess starts with weakening of the quadriceps andproximal limb musculature followed by altered me-chanical function of the patella and irritation to thearticular cartilage, resulting in pain and inflamma-tion of the joint. The presence of pain with in-creased joint effusion causes reflex inhibition of theextensor mechanism of the quadriceps musculature.Knee joint effusion results in arthrogenic quadricepsmuscle inhibition, which can increase loading aboutthe knee that may potentially increase the risk offuture knee joint trauma or degeneration.18 In hu-man studies, it is accepted that a few milliliters (30ml)18 of increased synovial fluid volume will inhibitproper firing of the quadriceps muscles, thus con-tributing to a downward cycle of muscle atrophy,pain, and degeneration of the joint health and func-tion. Excessive fluid of 60 ml in the knee jointshowed negative effects on the performance of thequadriceps muscles by decreased torque of 30% afterthe injection of fluid.19

Arthrogenic quadriceps muscle inhibition that ac-companies knee joint effusion impedes rehabilita-tion after knee joint injury.18 Quadriceps strengthand endurance are of vital importance for normalknee joint function, and therefore, restoring normalquadriceps function after knee joint injuries is anessential component of human knee rehabilitation.Persistent post-traumatic quadriceps weaknesspresents as a difficult clinical dilemma for the treat-ing clinician. An important underlying factor con-tributing to persistent, perhaps rehabilitation-resistant post-traumatic quadriceps weakness isarthrogenic muscle inhibition (AMI), which remainsunderstudied in current clinical outcomes researchin patients with knee joint injury.19 Quadricepsmuscle performance can be altered by exercising theswollen joint.

Consideration of alternative options, specifically aprogressive physical therapy intervention methodknown to resolve PFPS, could be of significant valuefor treatment of the biomechanical deficits of horsesafflicted with IUFP. This approach has specificguidelines for progressive advancement of exerciseand activity in avoidance of producing pain. Thisalternative approach of therapeutic exercise is a vi-able option to be considered by vets and ownersbefore more invasive procedures that have poor ev-idence-based results.4–7,15 Development of thisprotocol is based on experimentation in the field,literature review,3 a case study,20 and 12 clinicalcases of direct treatment along with reporting ofnumerous long-distance cases.





A commonly misunderstood approach of rest as atreatment for a mechanical problem such as IUFP isoften used by owners to prevent the horse fromexperiencing the catching or giving way or lamenessinduced by IUFP and UFP. This method is oppo-site of what is appropriate in terms of treatment forthis dysfunction. Muscle control is facilitated byneurostimulation of motor units, resulting in con-traction of muscle fibers. Therefore, some cases ofIUFP may result because of dynamic neuromuscularcontrol deficits. The method to address such dys-function is to increase the input into the neuromus-cular system with dynamic increased exercise.Specific ascending exercise, focusing on specific mus-cle function and controlling pelvic limb muscles ofthe hip and stifle flexion and extension patterns ofmovement is the main focus of this therapeuticintervention.

Quadriceps strength and endurance are of vitalimportance for normal knee joint function, andtherefore, restoring normal quadriceps function af-ter knee joint injuries is an essential component ofhuman knee rehabilitation. Persistent post-trau-matic quadriceps weakness presents as a difficultclinical dilemma for the treating clinician. An im-portant underlying factor contributing to persistent,perhaps rehabilitation-resistant post-traumaticquadriceps weakness is AMI, which remains under-studied in current clinical outcomes research in pa-tients with knee joint injury.19 Quadriceps muscleperformance can be altered by exercising the swol-len joint. Excessive fluid of 60 ml in the knee jointshowed negative effects on the performance of thequadriceps muscles by decreased torque of 30% afterthe injection of fluid.21

RationaleThe theory of delayed patellar release of IUFP be-cause of muscular atrophy and altered neuromuscu-lar response lends itself to commonly used humanphysical therapy methods of addressing knee dys-function, swelling, and pain. A treatment inter-vention of stretching tight structures followed bystrengthening weak muscles and increasing muscleendurance using neuromuscular facilitation tech-niques to improve proprioceptive awareness andskill in resumption of specific discipline retraininghas a significant role to play in the rehabilitation ofhorses afflicted with IUFP symptoms. The follow-ing method to treating horses with patellar instabil-ity is a humane approach that avoids increasingpain by inducing ascending strengthening exercisesin a logical progression based on approaches used inhuman PT to address human knee dysfunction.

3. Methods of Assessment

Before implementation of this program, it is impor-tant to have the horse properly evaluated by a vet-erinarian. Veterinary assessment by palpation,lameness evaluation, sonography, and radiographscan assist in a specific diagnosis. The symptom of

UFP/IUFP may be a primary problem or a secondaryfault related to another injury of the pelvic limb.A primary problem can be caused by skeletal growthspurts, conformational faults, poor shoeing/trim-ming techniques, or muscle weakness because ofinactivity. The problem of IUFP can be consideredsecondary if it arose later in the recovery phase froma systemic disease, limb injury, or surgery interven-tion, all of which will evoke weakness as a result ofmuscle inhibition and deconditioning duringrecovery.

After the horse is determined appropriate for PTintervention, the physical therapist will perform anassessment to determine the horse’s baseline status.PT assessment will start with a history from theowner. Owners report their horses to be clumsy,frequently stumbling, exhibiting tripping, or gettinga hind leg stuck behind. Sometimes, they reportthe horse’s hindlimb just giving out or collapsing.Often, an audible click or pop, known as crepitus orjoint noise, can be heard on weight shifting on andoff the involved leg. Observation of the horse’s con-formation and stifle angulation and muscular sym-metry should be noted.

On observation, these horses often present withan overweight body condition score of 6 of 9 points orabove, weakness of abdominal musculature, atrophyof top-line muscles, or generalized deconditioningalong with atrophy of hind-end musculature. Acommon finding of muscular asymmetry of the hindend is noted by viewing from the posterior in termsof gluteal height and width. Often, a hallowing ofthe musculature can be noted laterally below thetuber coxea on the affected side. On palpation ofthe lateral aspect between the tuber coxea and stifleregion, tissue depth is often shallow, allowing theexaminer’s fingers to sink deeper into soft tissues oftensor fascia latae, quadriceps, and bicep femorismuscles compared with the opposite side. Some-times, muscle fasciculations of the quadriceps andbicep femoris are exhibited. Sometimes, there isstifle joint edema present with pain responses andexhibited annoyance behaviors noted on palpation ofthe stifle.

More specific examination of the stifle joint canreveal visible jumping of the patellae when the horseinitiates a weight shift of stepping forward. Thisfinding is a pathological movement where the pa-tella is momentarily restricted on the trochlearridge, causing a jittering movement on its releaseover the medial femoral condyle. Under normalbiomechanical circumstances, this movement is asmooth gliding that should go unnoticed. Thesepathomechanics inhibit proper forward locomotion,often presenting with a resultant shortened cranialphase of step length at walk and trot.

Additional assessment involves taking the horsethrough flexibility testing. Often, the involved pel-vic limb is limited in passive mobility compared withthe non-involved limb, indicating shortening of soft-tissue structures surrounding the stifle and hip





joints. Mobility and stability testing can be admin-istered when lifting the non-involved pelvic limb offthe ground; one can observe how well and long thehorse can remain standing on the involved limb andwhat kind of muscle recruitment patterns the horseexhibits to remain standing. The examiner canweight shift or sway the horse over his weight-bear-ing limb to see how well the horse can stabilize andadjust to movement over that limb and thus, com-pare the results with the opposite limb.

Proprioceptive testing can be carried out by hav-ing the horse back in hand and perform turns on theforehand. Often, these horses will be resistant tothese maneuvers or exhibit clumsiness at foot place-ment. Often, at backing, the horse will drag theinvolved limb, take a shortened step length, andplace the limb in a more abducted position, causingthe path to deviate to the involved side. Turning onthe forehand, the horse may exhibit poor ability tocross midline with the involved limb, and often, thehorse will compensate with excessive pelvic obliq-uity rather than smooth cross over under the bellywith the limbs.

Last, for the assessment, gaits are viewed. Horseswith stifle dysfunction will show poor hind-endawareness, presenting as if their hind end is notattached to their trunk or seeming to be draggedalong by the forehand. Often, these horses do notstep up or track up well at the walk or trot. Thisobservation is most noted in the trot. Often, thehorses present with a Western jog at the hind end.Their front limbs are exhibiting full strides, but theback limbs have a much shorter stride, without thehind hoof coming up into the front hoof print (mal-tracking). On occasion, some of these horses mayexhibit forging from behind in which the hind hoofstrikes the fore hoof, but this finding is the lesseroccurrence in this author’s experience. Forging canbe an indicator of hind-end weakness and decreasedproprioceptive awareness, of which this pathologywould be attributed. These horses often exhibittrouble with cantering, such as running into thecanter with poor control, trouble picking up theproper leads, cross-cantering behind, using a four-beat canter, and having poor balance. All of theseproblems may be resultant of hind-end weakness,poor core strength, and possible joint pain.

The more muscular atrophy and poor neuromus-cular response of the extensor patellar release mech-anism, the greater potential irritation of thefibrocartilaginous patellar ligamentous extensionand degradation of retropatellar articular cartilage,which can lead to chondromalacia. McLellan etal.16 report that it is possible that chondromalacia inhorses goes underreported in the literature becauseof the difficulty in accurately diagnosing the con-dition. Radiography fails to show chondromalaciapathology. Nuclear scintigraphy localizes the dis-ease process to the femoropatellar region, requiringultrasonography to identify the pathologicalchanges within the affected joint.16 When this pro-

cess is present, the weakened limb will continue toget weaker without intervention. Thus, addressingthis downward spiral of events through PT has clin-ical significance in the prevention of degenerativechanges, leading to development of osteoarthritis,avoidance of more invasive procedures, saving offiscal resources, and promotion of functional resto-ration to prior level of performance.

Treatment Objectives of Stifle and Pelvic LimbStrengthening Program

1. Educate the owner regarding pathology,treatment approaches, and weight reduction.

2. Decrease pain and swelling of stifle joint.3. Decrease articular cartilage wear.4. Strengthen stifle musculature to optimize

patella mechanics and neuromuscular reflex.5. Increase overall conditioning (flexibility,

strength, proprioception, and endurance) ofthe hind end, abdominals, and top-line mus-culature.

6. Return to function for safe locomotion andriding back to the prior level of functionalperformance.

IndicationsIndications for use of this program would be stifledysfunction presentation of pain, swelling, mechan-ical symptoms of UFP/IUFP, proximal pelvic limbmuscle atrophy, shortened stride, abduction gait de-viation, decreased flexibility, proprioceptive deficits,recovery from pelvic limb injury, pain post-surgery,recovery phase of systemic diseases, and generaldeconditioned status.

ContraindicationsContraindications are insufficient physical exami-nation or diagnostics to rule out clinically significantmedical or surgical conditions that would be bettermanaged with traditional veterinary approachesalong with obvious conditions such as hoof abscess,joint integrity problems, presence of loose bodies,osteochondrosis dissecans lesions, subchondral bonecyst, fractures, neoplasm, and excessive pain thatprevents weight-bearing on pelvic limb.

4. Objective Measures of Success

Long-Term GoalReduce the number of audible clicks or visual jumpsof the patella in 10 weight-shift movements withinan 8-wk period.

Short-Term GoalIncrease tolerance to lateral tail pull isometric exer-cises to holding 10 s for 10 repetitions. Establish abaseline of tolerance on first assessment session.

5. Treatment: A Systematic, Progressive TherapeuticExercise Program

Success of this program is owner-dependent andlabor-intensive. This rehab protocol is a high-





energy expenditure undertaking for the owner.Treatment should be carried out daily for adequateimprovement to be noted.

The first method of intervention starts with edu-cation of the horse owner. The area of educationmost needed to owners is the revelation that af-flicted horses need more movement rather than lessmovement, such as stall rest. Stall rest is onlywarranted if determined necessary by a veterinar-ian. More movement is necessary in terms of dailymobility outside of a box stall as much as possible.Owners may need to consider moving their horses tomore desirable facilities to address the requirementsof this program.

Containing horses in box stalls is equivalent tohumans remaining on bed rest (BR). Deleteriousresults are known for humans staying on prolongedBR. Periods of limb unloading, whether producedby BR or spaceflight, have been shown to inducemuscle atrophy and loss of force and power. Thelatter always exceeds in volume loss attributed to aselective decline in myofibrillar protein.22 Korte-bein et al.23 indicated that 10 days of BR results ina substantial loss of lower extremity strength,power, and aerobic capacity and a reduction in phys-ical activity; therefore, the need for interventions tomaintain muscle function during hospitalization orperiods of BR in humans should be a high priority.23

Horse owners and veterinarians need to understandthe importance of minimizing stall rest and instead,providing the daily ongoing movement necessary tohalt the progression of pelvic limb muscle atrophythat often occurs after injury. It is essential thatowners understand that IUFP etiology often stemsfrom muscle weakness of inactivity and that atrophycontributes to biomechanical faults of the patellafemoral joint.

The following suggestions increase mobility ofsedentary horses. Keep horses moving throughoutthe day. Allow 24-h access from shelter to turnout.Ideal turnout consists of large, expansive pasturesinvolving slight hills. Have a companion animal,horse, or pony to maximize the herd instinct. Onehorse will always dominate the other to keep themmoving and foraging.16 Provide multiple feed pileslong distances from one another to keep horses mi-grating around the paddock from pile to pile.

Many clients have concerns if their horse has painwhen afflicted with IUFP. There is not verificationof pain presentation in current literature regardingIUFP. When less than ideal biomechanics occur, itis certainly imaginable that pain could result. Car-tilage itself does not have nerve endings. Pain willresult on disruption of retropatellar articular carti-lage or irritation of the MPL fibrocartilaginous ex-tension lodging on the medial condyle. Whenstructures misalign and malfunction, pain is oftenthe result from tissue irritation, setting off chemicalmediator release and resulting in inflammation.The presence of repeated misalignment, inflamma-tion, and pain sets off muscle response of inhibition

and spasm, contributing to additional downwardspiraling of pathomechanics. Therefore, it is prob-able and clinically relevant that pain is an issuewith some horses. When pain is present, it is nec-essary to address pain and inflammation with ap-propriate medications prescribed by veterinarians.

Neuromuscular alterations, including decreasedvoluntary quadriceps activation, are commonly as-sociated with knee osteoarthritis.24 AMI is aclinical impairment characterized by reflexive in-hibition of the motor neuron pool in uninjuredmuscle surrounding the injured joint. This oc-currence decreases the ability of the muscle torecruit motor neurons during contraction, limitingthe potential force that a muscle can generate as aprotective mechanism to decreasing excessiveforce around an injured joint. Prolonged deficitsof muscle activation through AMI, along withmuscle weakness, may decrease shock absorptionattenuation at the knee, leading to the increase ofjoint surface breakdown.18

Atrophied muscles can also be a source of pain.Muscle pain is associated with decreased motor unitdischarge rate during constant force contractions25

such as isometrics exercises. Motor unit recruit-ment strategies are altered during pain to maintainforce despite reduced discharge rate.25 Becausedischarge rate is a determinant of force, other adap-tations in strategy (possibly modulation in both cor-tical and spinal reflex mechanisms) must explainforce maintenance during pain.25

A variety of PT modalities and interventions canbe quite helpful in addition to pharmaceuticalintervention. Use of cryotherapy is beneficial atreducing pain perception and inflammation simulta-neously. Modalities of heat and ice are significantfor the reduction of pain, swelling, and musclespasm. The use of electrical stimulation known astrancutaneous electrical nerve stimulation (TENS)can help mediate afferent pain impulses. TENSapplied to human knee joints with osteoarthritis hasbeen reported to disinhibit AMI of the quadriceps.26

The roles of therapeutic ultrasound, laser, and elec-trical stimulation are well-supported by research forthe potential to increase healing of tissues and de-crease pain. Manual techniques such as massageto soft tissues can increase blood flow and decreasespasm. Joint mobilization can also decrease painand regain accessory joint motion to promote pain-free range of motion. Therapeutic ultrasound,pulsed electromagnetic fields, and low-level lasertherapy have been shown to increase collagen syn-thesis in fibroblasts, thereby increasing tensilestrength of tissues.27 Modalities and manual ther-apies should be considered and used to relieve painand inflammation while implementing an exerciseprogram to promote faster recovery to function.Decreasing pain will allow the horse to move morefreely into the exercise phase of rehab.





6. Therapeutic Stretching Program of Pelvic Limb

After minimizing pain, the first exercise approach ofthis program is to address flexibility by stretchingexercises of the hindlimbs. Tight muscles and soft-tissue structures can cause pain and weakening oftissue and contribute to abnormal biomechanics ofsurrounding joints.28 Stretching has shown reduc-tion of muscle atrophy and induced hypertrophiceffects in muscle.29,30 Addressing flexibility of thesurrounding hip and stifle muscle is important forgaining full range of motion, promoting proper skel-etal alignment, and maintaining correct biomechan-ics of joints. Stretching before participation inathletic activities is standard protocol for manyhuman sport training sessions,31 and it can reducethe risk of injury32 and enhance performance.27

Stretch routines for horses are also becoming morewidespread, probably reflecting the positive findingsfrom research on human athletes that indicate po-tential increases in muscle force, jump height,speed, range of motion (ROM), muscle length, andflexibility.31,33

There are many texts (Porter,34 Bromiley,35 andDenoix and Pailloux14) written about equine stretch-ing with instruction for stretching of limbs, neck,and trunk. Unfortunately, most texts do not indi-cate proper hand holds to minimize overstretching ofmultijoint muscles and tendons. Also, they do notsuggest the proper time to hold stretches to allow forphysiological lengthening of the muscle tendonousfibers, and they do not address the required fre-quency for repetition. A study done by Rose et al.33

addressing hindlimb stretching comprised of ham-string stretch, stifle and hip flexor stretch, andlateral quad stretch; stretches were applied twotimes, held for 10 s initially, and then, held for 20 s.Bandy et al.36 suggest, “Change in true flexibility(physiological lengthening of the fascicles) is depen-dent on the duration and frequency of stretching.”Therefore, Bandy et al.36 suggest maintaining pas-sive stretches for 30 s or longer as tolerated foroptimal relaxation and lengthening. They go on tosuggest that each stretch be repeated three times toallow for the most advantageous physiologicallengthening.36 Bandy et al.36 suggest that clientsrepeat these stretches daily to all muscle groups astolerated for the first 6 wk and then decrease fre-quency to every other day as necessary.

Findings by Rose et al.14 in 2009 indicated thathorses that were stretched 6 days/wk may have ex-perienced delayed onset muscles soreness (DOMS)from the passive stretching, and they may not havehad sufficient opportunity to recover (betweenstretching treatments) and adapt compared with thehorses that were stretched only 3 days/wk, thusexperiencing decreased stride length. These re-sults suggest that stretching every day may not beappropriate for the horse but that stretching 3days/wk (3DSR) may provide some benefit in termsof ROM.33 “The stifle and other joints showed a

significantly lower ROM after the 6 days of stretch-ing (6DSR) than after the 3DSR. The lower ROMresults could indicate that the 6DSR induced in-creased muscle stiffness compared with the3DSR.”33 The aim of stretching is to lengthenshortened tissues in an attempt to increase ROM,and therefore, the lengthening of the muscle fibersmay cause DOMS. The 6DSR group could havebeen experiencing DOMS from the stretching treat-ment, and they may not have had sufficient oppor-tunity to recover (between stretching treatments)and adapt compared with the 3DSR group.33

Rose et al.33 currently instruct clients to begin astretching program daily or as close to daily as pos-sible to start making positive gains as quickly aspossible if decreased hindlimb flexibility is noted.The results shown by Rose et al.33 suggest thatstretching every day may not be appropriate for thehorse but that stretching 3DSR provided somebenefit in terms of ROM. These findings merit ad-ditional consideration by this author. In this pro-gram, clients reduce the stretching regimen down toevery other day at around 6 wk because of the in-troduction of more aggressive strengthening exer-cises and consideration of time requirements tocarry out all activities.

Besides the lengthening effect that stretching hason surrounding tissues, promoting greater freedomof movement and increasing range of motion, thereare other advantages of stretching. Sharma andMaffulli27 indicate that stretching increases colla-gen synthesis and improves collagen fiber align-ment, resulting in higher tensile strength of tissues.Therefore, stretching may have positive contribu-tions to restoration of stifle joint biomechanicsthrough tensile strengthening of the surroundingsoft-tissue structures.

There are four specific stretching techniques thatthis author has found advantageous in treatment ofhorses afflicted with stifle dysfunction. This au-thor has thought that horses with stifle injuries mayhave learned response to avoid full flexion action atthe hip and stifle and therefore, may resist full flex-ion patterns of the involved limb, resulting in toedrag and a shortened cranial step length. There-fore, in a stretch called high flexion, which is shownin Figure 1, the limb is brought up passively into afully flexed hip and stifle position and held for 10–30s, and it may restore full flexion motion. Bringingthe affected limb up into a total flexion pattern toend ranges of hip, stifle, hock, and fetlock flexion byholding at the hoof and hock allows the horse torecover joint memory of full flexion sensation, re-minding the horse that he can move his leg up intofully flexed positions. This process can also assistwith providing synovial lubrication of joint surfacesand abolishing adhesions that may restrict end-range comfort.

The next stretch is in the protracted position bybringing the limb forward under the horse’s belly.This stretch is proposed to place tension on the





hamstring muscles of biceps femoris, semitendino-sus, and semimembrinosus along with middle glu-teal and deep gluteal muscles and possibly take upslack of the sacrosciatic ligament.37 By keeping thestifle and hock in extension, one may also stretch thegastrocnemius, soleus, and Achilles’ tendon.37

Bringing the limb into retraction is proposed tostretch the quadriceps complex, tensor fascia latae,sartorius, and gracilis muscles along with possiblythe long digital extensor more distally.37 Manytherapists hope that the iliopsoas and iliacus may beaddressed in this maneuver, but research is notavailable to indicate if these deep hip flexor musclesare affected in this maneuver.

Some horses that have had long-term stifle inju-ries can sometimes adopt a circumferential abduc-tion gait. This gait could arise for two reasons:a method in avoidance to flex the stifle and hip jointssecondary to pain or reduced range of motion oradapted tissue tightness of the lateral muscles ten-sor fascia latae and biceps femoris, restricting pro-traction of the limb. Therefore, stretching thehindlimb into adduction by crossing midline underthe horse’s belly can stretch out the tight lateralabductors responsible for inducing an abductiongait.

7. Therapeutic Strengthening Exercise Program

If the veterinarian has cleared the horse for physicaltherapy and assessment determines that there is nodeterrent to weight-bearing on the involved limb,then exercise should be considered the first ap-proach to intervention. The most logical approachto strengthen the hind end is to start with the small-est motion method of muscle work, which is isomet-ric contraction. Isometric exercise is a static formof exercise that occurs when a muscle contractswithout change in length of muscle or without visi-ble joint motion,28 which results in tensing or tight-ening of the muscle. For adaptive changes to occur,

such as increase in strength and endurance, contrac-tions need to be held for 6 s. This process allows forpeak tension to develop for metabolic changes tooccur within the muscle.28 The cognizance of per-forming an isometric approach at this point overisotonic activities that involve joint movement isparamount in the avoidance of causing joint pain.

The challenge in working with horses is that wecannot ask them to contract their quadriceps voli-tionally by verbal request, which we can do with thehuman patient. Often, the horse with stifle prob-lems will opt to rest the involved or atrophied limbfrequently. This rest allows or feeds into the com-monly known adage in PT that the weak get weaker,further facilitating the problem of non-use of theweaker limb. Asking the horse to do an isometricby weight shifting, the muscles around the hip andstifle will contract, providing joint stabilization.Stability in the stifle joint is controlled by a combi-nation of its mechanical restraints (e.g., ligaments,joint capsule, and bony geometry) and dynamic re-straints (muscles) mediated by the sensorimotor sys-tem, including proprioceptive feedback of jointposition and neuromuscular control.38 Weight-shifting exercises facilitate neuromuscular input tomaximize isometric and cocontractions surroundingthe stifle joint

An isometric contraction can be easily initiated byweight shifting the pelvic weight onto the involvedor atrophied pelvic limb by an exercise termed alateral tail pull (LTP) (Fig. 2). Isometric exercisesare excellent for recruiting muscle motor units andbiasing muscle without imposing pain from jointmovement. Joint pain can produce a reflexiveinhibitory response to the surrounding muscles.

Fig. 1. Passive high flexion stretch.

Fig. 2. LTP isometric exercise.





Muscle atrophy can also cause muscle pain. Mus-cle pain is associated with decreased motor unitdischarge rate during contractions. Motor unit re-cruitment strategies are altered during pain tomaintain force, despite reduced discharge rate.25

Therefore, imposing isometric strengthening exer-cises on the supportive muscles around the hip andstifle will increase strength, aid in shock absorptionand general condition, which can minimize addi-tional injuries,24 and halt atrophy. These exercisesshould be added one at a time to properly monitorfeedback and objective measures of swelling, endur-ance tolerance, and ROM.39

To perform LTPs, stand to the side of the horse at90°, have the horse in a squared position, grasp thetail at mid-length, and gently pull the horse’s pelvisover the involved hindlimb; this process is shown inFigure 3. This process will induce contractions oftensor fascia lata, quadriceps, and bicep femoris.Often, the gluteals and lower abdominal obliquemuscles will fire as well. Hold for 10 s for 10 rep-etitions. It can be helpful to pre-occupy the horsewith grain, hay, or grooming if they become agitatedwith this exercise. This preliminary exercise is ini-tiated on day 1.

Many owners ask if the horse needs to remain in asquared position to perform this exercise. The an-swer is that they do not. Strength will increaseonly at the joint angle at which the isometric exer-cises are performed.28 Therefore, to developstrength of the hindlimb, the aim is to develop

strength functionally in all positions common to thehorse. Horses do not always stand square. There-fore, this isometric toning process by LTPs should bedone in all positions that the horse stands to developstrength throughout the range of motion.

To progress isometric demands from the LTP, cli-ents are instructed at a single leg standing exerciseto promote stability of the involved limb. This ex-ercise is done by picking up the opposite hindlimb asif to pick out the hoof. One must be mindful of notallowing the horse to rest his weight on the handlerbut rather, to make him maintain his weight on hisinvolved limb for 10–30 s or more as tolerated.This exercise will ask the horse to build his musclecocontraction tolerance and endurance, promotingstability of the pelvis, hip, and stifle joints. Afterthe horse has been through the previous exerciseregimen for about 1 wk, many owners notice im-provement of the horse’s tolerance to LTP durationand repetitions along with increased tolerance tostretching. The next step in this program is pro-gressing into isotonic (dynamic) exercise. Isotonicexercise involves the concentric (shortening) and ec-centric (lengthening) muscular contractions that re-sult in movement of a joint or body part against aconstant load. The load28 (resistance) of isotonicexercise is gravity pulling on the horse’s body andlimbs while in locomotion. Load can be increasedby a rider’s weight, walking through mediums ofwater or snow, pulling a carriage, or workingagainst Theraband (TB).a

Isotonic exercises begin with hand-walk-ing. Many horses walk with as little energy expen-diture from behind as possible. This prescribedhand-walking regimen requires significant impul-sion. For horses to make strength and endurancegains, they need to learn an improved manner ofwalking forward with impulsion coming from theirhind end so that their hind foot tracks up into theirfore hoof print. This walking may require sometraining with the owner as to how to ask and imposea forward walk with impulsion. A specific distanceor time is assigned dependent of what level ofexercise to which the horse is currently accustomed.It is ideal to carry out the hand-walking withimpulsion before the passive stretching exercisesfor warming up soft tissues to increase tissueextensibility.

If the horse is tolerating the progression, backingin hand is introduced next, which is seen in Figure 4.Here, focus is again on good stride quality. Thisfocus means that the horse should willingly pick upthe involved limb without dragging it or abducting itand place it with an even step length behind him.To start, a specific distance of 10 ft is reasonable forthree repetitions. Many horses do not willinglywish to back. Directly behind them is their oneblind spot. Therefore, training with the owner inhow to ask for and reinforce this method may beneeded. Progress to longer lengths of 20 ft on levelground for 5-min intervals as tolerated daily for 1–2

Fig. 3. Stand 90° from the horse’s involved pelvic limb and pulllaterally to displace weight on that limb.





wk. A small crop or dressage whip can be helpful tohave on hand for reinforcement.

The progression in the program continues byhand-walking up and down slight inclines. Gradi-ents are the foundation of equine strength train-ing.40 The therapist has to look about the facilitygrounds to find the adequate hill available. Some-times, this hill is non-existent or less than desirable.Therefore, specific guidelines are hard to prescribethat are appropriate for each case scenario. It isrecommended that this progression start graduallywith two or three trips up and down to start at 5-minintervals for up to 15 min daily for hill work astolerated. Clayton40 advocates walking up gradi-ents as ideal strengthening activity in horses thathave unilateral hindlimb weakness. Gradually in-crease to steeper inclines as tolerated. Documentinclines, distance, tolerance, and progression.

The chart shown in Table 1 is an example of theflow sheet handout given to clients to track theirhorse’s progress and tolerance.

A variable introduced next is surface vari-ety. There are many reasons for this variable.Introducing a variety of surfaces provides tactileand proprioceptive input into the horse’s sensorisys-tem. Consider how much time most performancehorses spend going around and around on the samelevel surface in the ring. This author believes thathorses that do mainly ring work accommodate to theanticipation of the common dependable surface thatthey do not need to think about for their next foot-fall. If there is no variability in terms of surfaces,obstacles, and inclines, their sensory feedback sys-tem may accommodate to the expectation of con-stant footing. By introducing the horse to a varietyof surfaces, such as asphalt, wood chips, sand, mud,

Fig. 4. Backing in hand exercise.

Table 1. Example of the Flow Sheet Handout Given to Clients to Track Their Horses’ Progress and Tolerance

Stifle Protocol Exercise Flow Sheet

Exercise date hold secs reps

Lateral Tail Pulls

Opposite Leg Lifts

Walking in hand

Backing in hand

Hills

Walk/trot transitions

Long-lining

Stretching:

Protraction

Retraction

Adduction

High flexion

Fig. 5. Hand-walking up and down inclines.





gravel, and ground poles, he will receive differentproprioceptive and kinesthetic feedback at the hoofand phalangeal joints. This input will stimulatethe sensory feedback system, facilitating a neuro-muscular response to prepare for whatever changesin surface appear.

After about 2 wk of the above program and reas-sessment, the next progression step is walk to trottransitions in hand. The focus is on quality longstrides behind with accelerating transitions upand controlled transitions down from trot to walk.Down transitions emphasize eccentric control of thehip and stifle muscles essential for conditioning40 forimproved stifle function. Muscles develop thegreatest tension when they perform eccentrically.40

Eccentric exercise can increase collagen, tensilestiffness, and strength.27 Eccentric contractionshave been found to cause minor damage to musclefibers and may produce DOMS40; therefore, somehorses may become a little more stiff in this phase.Dependent on the horse’s level of fitness, a numberof transitions are again decided for use as a baselineand documented on which to build. As the horsetolerates this progression, the owner can increase astolerated. Good-quality up and down transitionsmust be demanded from the horse to maximize mus-cle recruitment and rewrite the previous motorplans of poorly controlled transitions.

The following progression of exercises is purpose-fully abridged (not explained in full detail) becauseof the author’s effort at reducing the length of this

paper. The exercises are introduced according tothe horse’s tolerance to the previous activities ofthe program without showing signs of regression,increased pain, swelling, stiffness, or lameness.These exercises and activities increase demand onthe horse in terms of isotonic work, eccentric control,and introduction of coordination and skill. Many ofthese horses, because of injury, weakness, anddeconditioning, lack good motor control of thehindlimbs. Often, they have poor motor planningand faulty foot placement along with poor lumbopel-vic control. Therefore, these exercises are selectedto also recruit thoracolumbar epaxials, abdominals,and pelvic muscles.

Turn on forehand (TOF) in hand in both directionschallenges the horse’s flexibility of the lateral pelvicmuscles and coordination at crossing midline withhindlimbs. Many horses with stifle dysfunctionlack good motor control at this movement. Com-pare one side to the other side in terms of willing-ness and fluidity in motion. They improve rapidlywith repetition of this activity.

Backing in hand up and down gentle inclines forshort distances of 10–20 ft requires gluteal recruit-ment, weight shifting, flexion, and extension of thelumbopelvic region, thus demanding increased con-trol of the patellar extensor release mechanism.Clayton40 advises that alternating between forwardmovement, halt, and backing on downhill gradientswill improve both strength and balance.

Progression to lunging activities can be considerednext. Given the option of the horse standing idle orgetting exercise, Clayton40 advocates: “Movement isbetter than no movement.” Lunging, long lining,and posoa work are all ways to get the horse’s car-diovascular and musculoskeletal systems into con-dition before putting a rider’s weight on the horse’sback for ridden work.

Lunging by use of a halter and rope is discour-aged. Lunging a horse in this tack allows excessfreedom of movement and poor control of the horse.Often, the result of this setup encourages improperposturing. The horse often rushes his gaits, usingan elevated head looking to the outside of the circle,a hollowed shortened back, poor use of abdominals,off-balanced center of gravity, and increased weight-bearing on the inner fore and hind legs. Increasedweight-bearing and probable increased torque forceson the inside hind stifle joint are less than ideal forrehab purposes. Often, lunging a horse with just ahalter and rope allows the horse to swing his headaway for the handler, work off of the forehand, de-prive use of his hind end, have poor tracking-up, andhave reduced dynamic balance. This author dis-courages lunging in this manner.

Preference over lunging with a halter is use of along line or a posoa with full tack, bit, and bridle.These techniques encourage abdominal muscle re-cruitment and lengthening of epaxial muscles fordevelopment of proper self-carriage, thus facilitat-ing improved movement patterns and better propul-

Fig. 6. LTP on mounting block for contraction of stifle musclesin flexed position.





sion from the hind end. Using long lines (LL)allows the handler to have aids to the horse’s mouththrough bit, bridle, and lines, thus allowing in-creased control over the horse in terms of bending ona circle properly, creating impulsion from behindinto the bit, and recruiting better use and develop-ment of the top-line and hind-end muscles. LL willencourage the horse to come up under himself andround throughout the top line, thus encouragingproper use of his hind end in a more flexed positionthrough the croup. A step up from LL would be useof a posoa. Posoas are helpful for encouraging thehorse’s proper carriage by stepping up into the cra-nial aspect of gaits from behind. Posoas requiresignificant training to use properly. Improper usecan lead to fatigue and injury. Large circumfer-ence circles are again required to avoid increasedtorque stress on the stifle.

The use of intermittent ground poles requires in-creased flexion of the hip, stifle, and hock while inmotion. Ground poles can also help improve pro-pioceptive awareness of limb placement, improvingcoordination of fluid movement patterns and bal-ance. They can be placed in a variety of methodsfrom well-measured distances haphazardly ar-ranged to encourage the horse to look and place hisfeet carefully with adaptation to his stride lengths.In a study conducted by Holler et al.41 of caninestraveling over ground rails, they determined that anincreasing flexion range of motion of the stifle andhock were evident. For the horse recovering fromstifle dysfunction or pelvic weakness, the addition ofground poles or cavelettis can be an excellent activ-ity to promote propioceptive awareness of limbplacement and improve coordination of fluid move-ment patterns and balance.

Additional advancement in the progression usesany of the above exercises on hills. Hill progressionshould start with minimal slopes, building to mod-erate and extreme gradients. Long lining on a hillcan maintain the horse’s collected frame, while em-phasizing eccentric strength and control and ad-dressing many training factors at onetime. Careful progression and monitoring of theseactivities are essential to avoid fatigue, which willcause the horse to use undesirable compensationstrategies. Clayton40 suggests for horses withasymmetric weakness to work across a slope withthe weaker limb positioned on the upper side of theslope so that it works in a more flexed position.

After approximately an 8-wk period of the aboveexercise regimen, with noted reduction of IUFPsymptoms and no signs of lameness, the horse isappropriate for a riding trial. If the horse is able towithstand the weight of a rider, conditioning undersaddle, and slow progression of W-T-C on the flat,work may be progressed. Continuation of theabove exercises are done under saddle with transi-tions up and down at all three gaits, lateral work,TOF, rein backing, up and down hills, and groundpole work, and work is slowly progressed to caveletti

work as tolerated. These activities are all deter-mined in quantity and quality by the therapist anddocumented for tolerance and progression. Contin-ued variation of ground surfaces will challenge thehorse with coordination and foot placement. Theaddition of rider weight and forward locomotionthrough water, snow, or sand can act as resistance,increasing the training responses for strengthening.For horses that are trained for cart pulling, the cartis, again, an added resistance that the horse canbenefit from for strengthening the hind-endmuscles.

Frequently, some riding facilities and certainparts of the country do not have access to hills.Therefore, to replicate strengthening by hill climb-ing, a creative alternative is to position the horse’shindlimb in a flexed position on the step of a mount-ing block or sturdy elevated block and impose aweight shift or LTP. Dressage horses often do notwork on hills. It has been this author’s experiencethat many dressage horses with stifle dysfunctionbenefit from this program and the addition of cross-training with use of hills or caveletties to increasethe strength demand on the hind-end musculature.

The use of therapeutic training aids such as fet-lock jangles, TBs, and kinesthetic proprioceptivetapeb can be used creatively to affect the horse’ssensory feedback system to enhance and correct per-formance. By tapping into the equine sensory mod-ulation system through mechanoreceptors andproprioceptive systems, the physical therapist caneffectively enhance performance in many forms us-ing aids applied directly to the horse’s skin orbody.42

A TB is a useful strengthening tool in the humanclinic as well as the equine training arena. TB useis a resistive exercise system of stretching elasticband material, which provides an inexpensive andeasy way to train muscles concentrically and eccen-trically. The therapist can design TB exerciseprograms to provide resistance to a variety of bodyparts or any phase of motion desired.39 Used prop-erly, TB exercises can successfully achieve sport-specific strength and function of the musculature39

when placed around a weakened limb. For exam-ple, use of TB adds sensory awareness and resis-tance to the horse’s hamstrings on retraction of thehindlimb. Based on this author’s experience, resis-tance of the band at the horse’s hamstrings encour-ages the horse to step up and under belly more,flexing at croup to lengthen the hind-end stride intothe cranial aspect.

Kinesthetic proprioceptive taping techniques usedon humans enhance the sensorimotor system andhave been used clinically in horses for similar pur-poses. The aim of taping is to stimulate mechano-receptive and proprioceptive activity in the skin,fascia, ligaments, and joints. This taping affectsthe sensory afferent activity from that region, mod-ulating or altering neuromotor control of locomo-tion.43 Patellar taping has been shown to improve





joint control in pain-free humans with poor propri-oception of the knee44 and individuals withPFPS.45,46 Similarly, in human studies, the com-bined mechanical and proprioceptive benefits oftaping for prevention of ankle sprains as well asrecurrence of sprains is well-documented.47 Onestudy investigated the biomechanical effects of tap-ing the fetlock in the forelimbs of horses.48 How-ever, in this model, mechanical rather thansensorimotor effects were investigated, with resultssuggesting that changes seen might be a reflection ofproprioceptive adaptations. Effects on ground re-action forces as well and joint ranges of motion wereobserved, and additional research is warranted.43

Kinesthetic proprioceptive tape can be used to stim-ulate and recruit proximal musculature, providingtactile stimulation to facilitate elastic recoil of mus-cle in the early phase of swing.

Many horses that have stifle dysfunction tend toexhibit a toe drag of the involved limb. A method ofusing a lightweight bracelet jangle that providestactile stimulation to the horse’s pastern and coro-net band can induce a higher flight arc of the hoof,which was determined by Clayton et al.49 Tactilestimulation was provided by a lightweight (55 g)device consisting of a strap with seven chains thatwas attached loosely around the pastern.49 Resultsof their research indicated that peak hind-hoofheight increased significantly when wearing hindstimulators. The first trial with stimulatorsshowed the greatest elevation followed by a rapiddecrease over the next three trials and then, a moregradual decrease. Their research concluded that,to facilitate a generalized muscular response for in-creased stifle and hock flexion, a short burst of tac-tile stimulation is likely to be most effective,whereas longer periods of stimulation will be moreeffective for strength training.

The above training aids can be used in the latterparts of this rehab program. They should only beused under a careful eye by a trained therapist forevaluation of their success to address the specificobjectives. These devices are used to stimulate pro-pioceptive and sensory motor responses, and there-fore, they have the ability to be abused or overused.Under the wrong conditions of inexperienced han-dlers, they can be overused dangerously, leading tofatigue and DOMS. Therefore, it is recommendedthat they only be applied in appropriate conditionsby a trained physical therapist and provided forindependent use to clients who have a good under-standing of their application and conditions.

When they are asymptomatic, horses need tomaintain their strength gains and soundness by avigorous cross-training program. Therapeutic ap-proaches should continue, starting with allowing thehorse outdoor roaming as much as possible. Thesehorses should preferably be allowed as much timeout of their stalls as possible. Turnout in a fieldwith hills, slopes, and a herd mate is most optimal.A run-in shelter can be ideal, with more housing as

necessary depending on climate and weather. Theless that the horse stands idle, the better the out-come. To keep these horses in top condition to pre-vent regression, they should continue to be workedusing a variety of the above exercise regimens threeto four times a week. Intensity can and shouldvary with cross-training; on some days, address ringwork on the flat, and on other days, consider trailriding with hills and small jumps. Some daysshould address ground poles and jumping of a vari-ety of obstacles with variable heights. The stretch-ing program can be carried out post-exercise severaltimes throughout the week. The more demands onthe horse isotonically through ridden work or longlining with hill and ground poles, the less that theowner should have to keep up with LTP exercises.LTP exercises are a start that should not be neces-sary after the horse has progressed to more skillfulactivities as outlined above.

The effects of conditioning depend on intensity,duration, and frequency of the regular exercise.40

This program attempts to address each of these fac-tors by careful introduction and slow progression ofexercises. Conditioning exercises should be tai-lored to the requirements of the sport to simulateadaptive changes in muscle fibers.40 This idea is awidely accepted theory in terms of human physiol-ogy, referred to as the specific adaptation to imposeddemands (SAID) principle, which emphasizes theimportance of specificity of training to a skill.39

In general, endurance exercise enhances the aerobiccapacity but compromises the power and speed ofmuscle contraction. Sprinting activities enhancethe horse’s power and peak at the expanse of aerobicendurance.40 Therefore, in terms of a maintenanceprogram of exercise after rehab, a cross-trainingapproach should be carried out three to four timesper week.

8. Discussion

This program has been conducted by in-the-fieldclinical experimentation. It has been anecdotallysuccessful in that the majority of the clients thathave tried this approach with their horses have seenpositive improvements. At the time of this writing,this author has treated 12 horses directly in terms ofhands-on assessment and treatment. Please referto Table 2 to understand the signalment, discipline,and outcomes of each horse.

Each of the above-listed horses, two mules, andone miniature horse made improvement in terms ofdecreased symptoms and return to function. Referbelow to “Limitations” to understand the reasonswhy this author has difficulty in reporting quantita-tive outcome measures. One horse was started onthe program with good tolerance before veterinaryevaluation. After veterinary evaluation, radio-graphic diagnostics indicated that significant OAwas present, and the veterinarian advised the clientto terminate PT intervention, which was unfortu-





nate for this horse. The baseline for progression inthis program is based on initiation of the prelimi-nary goal of tolerating a 10-s hold at LTP exercisedone for 10 repetitions. All equines that reachedthis point showed a decrease in their IUFP symp-toms. On initiation of treatment, some horsescould not tolerate a full 10-s hold, and therefore,their baseline would have to start at 5-s holds, withonly five repetitions tolerated and progression astolerated. After a horse can tolerate a 10-s holddone 10 times, the criteria to move them on in theprogram as outlined was fulfilled.

Each horse presented as a different scenario pre-senting with different findings for baseline. Manyhad pre-existing or co-existing conditions of a vari-ety of diagnosis. Therefore, generalized outcomesare difficult to quantify and qualify because of thisreason of varied starting conditions of the involvedequines (uncontrolled variable) and various clientreasons for terminating treatment. Success wasbased on subjective views of the clients and objectivefindings listed below. Except in one case, wheretreatment was terminated by a veterinarian’s deci-sion, all other clients felt their equine made objec-tive gains of less frequency of IUFP and decreasedjumping of the patella on weight shifting and for-ward locomotion. Each equine had to achieve theshort-term goal (heralding achievement) toleranceto isometric LTP exercises, holding for 10 s for 10repetitions before progressing with the program.

Because of the nature of individual client econom-ics, each horse had different lengths of treatment.One horse received only 3 wk of direct supervision,whereas another horse progressed through a 2-yrprogram of supervised progression. It is difficult toprovide exact objective measures for each horse.Each horse started at a different baseline, and own-ers had different outcome goals dependent on theirdiscipline. Often, owners were the decision-makersas to when they felt that they had achieved theirpersonal goals with their horse and thus, would selfterminate. Another variable that plays a role as tohow quickly horses progress and achieve wellness isvery owner-dependent, because it depends on howmuch time and energy they put into this rehab pro-gram. Exercises are generated by facilitationmethods taught to the owner by the therapist forthem to perform daily. Many owners admit to notbeing able to do all prescribed exercises based ontheir physical stamina or time limits.

Of the 12 equines, 8 of them improved, reachingthe goals stated for progression, and they continuedwith the program back into their riding discipline.Two of the equines made no changes because ofpre-existing conditions, and two equines made ad-vances in the program and then later relapsed.The most common reasons for relapse or regressionwere winter in New England, leading to increasedtime of immobility, and lack of owner continuancewith the program.

Attainment of the following criteria indicates asuccessful recovery outcome:

● Owner understands pathology and has knowl-edge of IUFP and how to prevent recurrence.

● Reduction of audible clicking of the patella(from established baseline).

● No pain responses on stifle palpation.● No evidence of lameness with equal stride

lengths.● Noted increase in hind end musculature

(hypertrophy).● Increased flexibility of bilateral hindlimbs.● Decreased frequency of stumbling and tripping

occurrences.● Decreased occurrence of giving way of locking

up (UFP) of stifles.● Increased endurance to exercise tolerance to

perform 50–60 min ridden work.● Return to function at prior level of perfor-

mance and discipline.

This author has also had several long-distance cli-ents who attest that their horses, diagnosed withstifle dysfunction and pelvic limb weakness, haverecovered by using this program. These clients,treated by consultation and instruction of the pro-gram through electronic mail and phone conversa-tions, feel that they have made positive gains basedon the criteria listed above.

This author was unable to compare this programwith other similar programs because of the lack ofpublished pre-existing stifle programs found bysearching PubMed and a variety of other establishedveterinarian search engines. The common refer-ences to strengthening approaches were vague,stated, for example, by Miller and Swanson2 as “al-tering the conditioning program can be helpful … itshould include long, extended, straight exercises.Uphill work with limited downhill work in good foot-ing is encouraged.”2 Many other non-exercise ap-proaches have been documented regarding thepositive and negative evidence for a variety of treat-ments of IUFP. In terms of invasive procedures,the following points will compare and contrast thevariety of approaches versus the use of this thera-peutic exercise program.

Researchers do not seem to agree or have deter-mined if there is a laxity or tightening of the MPL tocontribute occurrence of IUFP. Both conditionshave been theorized. One approach to the theory ofthe ligament being too lax is to irritate it with caus-tic agents. The exact mechanism of irritant actionremains unknown; however, it is thought to causeinflammation and thus, tighten the ligament, hin-dering fixation on the femur.2 The use of 2% iodinein almond oil as a caustic agent to the MPL inducessevere inflammation and fibroplasia. Maturationof the inflammatory and fibrous response may con-tribute to resolution or attenuation of upward fixa-tion of the patella by subsequent stiffening of the





Tab

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Sig

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ent,

Dis

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and

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com

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plea

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5yr

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yes

draf

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smal

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ddoc

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colla

tera

lde

smit

isan

dm

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cal

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all

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fam

ilyhx

Mar

dres

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7w

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2yr

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yes

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yes

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prog

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Mas

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yes

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yes

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ine





ligaments.6 Caution should be considered becauseof concern of infection whenever injecting tissues,ligaments, and joints to injections. Injection ofcaustic agents mistakenly directed into the synovialstifle joints can cause articular cartilage breakdown,significantly damaging the animal’s potential for re-covery. If done correctly, irritation to the MPLwith the caustic agent will cause inflammation andpain to the stifle region for several days. Often,NSAIDs are not provided after MPL injections toencourage a full inflammatory process to dictate fi-brotic enlargement of the ligament.

Along the lines of injections, it is postulated thatsystemic estrogen relaxes the peripelvic musclesand ligaments, thus altering the angle of the pelvis.Alteration in pelvic angle may decrease the stiflejoint angulation and thus, enable the patella to re-lease from the femur.2 Miller and Swanson2 stressthe use of exercise in conjunction with estrogen ther-apy. They also state that this approach may beappropriate when used short term in the younggrowing horse or pony but that results are not long-standing.2 Applying this stifle strengthening pro-gram to a horse that has undergone either of theseinjection methods may improve their outcomes.

Unfortunately, the approach of MPD commonlyused over the past two decades resulted in patho-logic changes in the articular cartilage of the patellaand adjacent soft tissues.4 A controlled study de-signed to evaluate the effects of MPD, combinedwith exercise restriction, determined that entheso-phyte formation and lateral deviation of the patellawere found by radiographic evidence, concludingthat MPD leads to patellar instability. Fourmonths of stall rest did not prevent the lesionscaused by post-surgical patellar instability.15 Gib-son and McIlwraith4 conclude that the use of thissurgical procedure should be reserved for only themost persistent and confirmed cases of UFP.4

In human orthopedic intervention, ligament re-section is rare. To restore proper joint biomechan-ics, human clients are referred to physical therapyfor strengthening of surrounding musculature andstretching of tight soft-tissue structures. There-fore, this stifle rehab program may be a preferredmethod of treatment to minimize MPD in equines.

Dumoulin et al.7 suggest that an approach of CTSwas fully successful in 51.6% of the horses afflictedwith IUFP and that a longer convalescence period of3 mo after MPD is desirable. Results indicate thatconservative treatment, with special attention forCTS, is worth trying before performing more radicalprocedures to correct UFP.7 Another surgical butless invasive approach to desmotomy is pre-cutane-ous splitting of the proximal one-third of the MPL,and it has been found to be a very effective treat-ment for UFP and allow for rapid return to normalactivity.5 Tnibar5 proposes that imposing isomet-ric strengthening, hindlimb stretching, and hand-walking during this time of convalescence may

provide improved outcomes over stall rest alone forall post-surgical situations listed previously.

Stall rest confinement is discouraged because ofpotential loss of muscle tone.2 Lack of exercise, inthe form of stall rest, generally delays the develop-ment of equine musculoskeletal tissues. In a studydone by Xie et al.13 regarding horses afflicted withdistal suspensory ligament desmitis (DSLD), exer-cise did not exacerbate but rather, may have im-proved signs of DSLD in mild to moderate cases.

Sometimes, rest is necessary for structures toheal. For mild cases of ligamentous and/or menis-cal damage without gross tearing or rupture of thestructures, Jeffcott and Kold8 reported that horsesresponded satisfactorily to rest. Knowing that ex-ercise is an important factor in the biomechanicalstrength of tissues, it is a potentially powerful toolfor the enhancement of injury recovery.50 Isomet-ric exercises can retard muscle atrophy in earlystages of rehabilitation when immobilization is nec-essary to protect healing structures.28 Therefore,during periods of stall rest, this author advocatesthat veterinarians and owners consider the benefitsof isometric LTPs to avoid proximal muscle atrophyand stretching to increase tensile strength of sur-rounding tissues.

Stability of the stifle joint is controlled by a com-bination of its mechanical restraints (e.g., liga-ments, joint capsule, and bony geometry) anddynamic muscle restraint mediated by the sensori-motor system, including proprioceptive feedback ofjoint position and neuromuscular control.38 Tomaximize performance and minimize injury, it isimportant to understand and apply the principles offunctional adaptation of skeletal tissues (bone, car-tilage, tendons, and ligaments), which differ in theirresponses to changes in mechanical environment.To keep the equine musculoskeletal system primedduring periods of recuperation, it is essential to keepsome tension on tissues to avoid decline. This ten-sion can be imposed during the equine’s recovery byisometric strengthening and stretching protocols tominimize downward decline to development of IUFPsymptoms while horses are on stall rest, are recov-ering from disease, or during long winters. Withappropriate monitoring of exercise programs, own-ers, trainers, therapists, and veterinarians can ap-ply the science of functional adaptation to thetraining demand for equine athletes to improveequine health and improve outcomes.

The use of therapeutic aids such as TB, kines-thetic proprioceptive tape, and a variety of fetlockstimulators or lightweights should be considered fortheir therapeutic input into the horse’s sensory sys-tem. These products can be used during the middleto later part of this program to ask more from thehorse during isotonic training, whether it be inhand, on long lines, or under saddle, for increasedmuscle facilitation. Often, horses that have beenlame for a long period may need additional input tofacilitate increased stride length or heightened flex-





ion pattern that they have forgotten to use. Clay-ton et al.49 recommend application of thestimulators for short periods (e.g., trotting 50–100m) when the goal of rehabilitation is to maximizemuscle facilitation.49 If rehabilitation is beingused to mobilize the joints or improve strength orendurance of atrophied flexor muscles, longer peri-ods of treatment (e.g., trotting 200–300 m) are moreappropriate.49

Many horses with IUFP present with asymme-tries that can lead to circumduction gaits and ashortened stride length. Tight structures can alsoalter biomechanical stresses around joints, such asthe patellar femoral complex. This program advo-cates a regimen of stretching of the horse’s pelviclimbs daily. As proposed by Rose et al.,33 stretch-ing daily may be too intensive and cause delayedonset of muscle soreness. This author will considerthese findings in additional development of this pro-gram. Additional examination of stretch frequencymay establish its potential to enhance performanceand welfare.33 A theory proposed by Schuurman etal.51 in 2003 is that an overactive vastus medialismuscle may be a culprit of IUFP. Through theirresearch in vivo, they claim that, during weight-bearing, only the vastus medialis but no other mus-cle was active, providing the necessary traction tostabilize the stifle.51 The required tension was es-timated to be less than 2% of the force that would beneeded in absence of a lock mechanism.51 Theyconclude that diagnosis and treatment of patellarfixation should include the possibility of an overac-tive vastus medialis muscle as a possible cause ofthe disorder.51

In human PT, treatment of a post-surgical or re-cently sprained knee or PFPS involves treatmentinitiated with pain and inflammation reductionmethods and modalities along with attempts to pre-vent additional atrophy of the quadriceps by start-ing the patient on isometric quadriceps settingexercises. Isometric setting exercise of the quadri-ceps is performed by positioning the knee in exten-sion; then, the patient actively tightens thequadriceps muscles for a 10-s hold. Patients arestarted with the least pain-producing exercise ofisometrics, then slowly progressed into range of mo-tion and stretching exercises, and later, progressedinto weight-bearing closed kinetic chain exercises.Last, skill-related activities, such as kicking a ball,are introduced using proprioceptive feedback strat-egies to regain coordinated movement.

There is a specific progression to imposing exer-cise in avoidance of pain, such as starting astrengthening regimen with isometric contractions,then moving into isotonics, and last, focusing oneccentric control and skilled coordination. A pa-tient with an acute knee condition, accompanied byinflammation, atrophy, and pain, would not be ex-pected to fully weight-bear, climb stairs, or run up ahill. It would be considered malpractice to have aknee-injured patient begin PT with a regimen of

stair- and hill-climbing activities under these condi-tions. Excessive patellofemoral compressive forcescan lead to additional patellofemoral pathologies,such as chondromalacia or osteoarthritis.9 There-fore, this author proposes that horses with stifledysfunction should not be asked to initiate rehab byclimbing hills when they may have a painful stiflejoint surrounded by weakened and inhibited pelvicmuscles.

PTs have much to offer in the realm of rehabilita-tion strategies, with expertise in the practice for thetreatments of injury for promoting the best recoveryof animals after catastrophic injuries. Education ofthe animal’s owner is the first and foremost signifi-cant objective to achieve. This program scenariopresented a common human error to want to stallrest an injured horse in prevention of them hurtingthemselves further. This rest is a widespread mis-conception, especially in the realm of IUFP. Own-ers need to understand the relationship betweeninactivity and muscle atrophy. IUFP pathologycan be linked to the horse’s poor condition of muscleatrophy. Therefore, engaging owners in this ag-gressive and demanding approach is vital for theirhorses’ recovery from symptoms and prevention ofrelapse by use of a cross-training approach afterrehab.

Horses represented in the chart did not warrantthe role of modality use. They were struggling withIUFP because of primarily deconditioning, post-sys-temic diseases such EPM, or post-surgical chronicityof poor motor patterns of gait. None of them werein acute phases of healing or pain. One modalitythat could play a significant role in aiding in painand edema reduction of acute-phase horses withIUFP would be that of electrical stimulation (E-stim). The use of E-stim can be very versatile forIUFP. During the acute phase, E-stim can assistwith edema reduction around the stifle joint.TENS applied to knee joints has been reported to notinhibit the quadriceps’ arthrogenic muscle inhibi-tion.24 In desire of muscle contraction, such as iso-metrics, E-stim can be used to recruit a larger numberof motor units for stronger contractions. This modal-ity, versatile and well-supported in the research,24 canbe very advantageous in the multifold treatment ofIUFP.

The role of propioceptive training plays a signifi-cant role when treating the equine. The feed-forward and feedback loops of facilitatedneuromuscular control apply to strengthening andmotor-relearning progression. Deficits in neuro-muscular reflex pathways as a result of decreasedproprioception have been shown to have a detrimen-tal effect on joints. Proprioceptive rehabilitation tofacilitate dynamic joint stabilization is thought toimprove the neuromuscular control mechanism.51

The area of propioceptive neuromuscular facilitation(PNF) by PT expertise compares with no otherequine practitioners, because PTs are experts in thestudy of and application of movement science with





use of skilled manual cueing. Application of kines-thetic proprioceptive tape can be used in conjunctionwith PNF to aid sensory afferent activity, thus mod-ulating or altering neuromotor control of locomotion.This clearly appropriate area for equine research islimited to date.43

In consideration that some horses may not beprescribed the proper rehabilitation treatments toaddress IUFP or may not respond favorably, therewill be some horses subject to more invasive proce-dures such as sclerosing injections or MPL surgery.With the stifle joint of a horse’s hindlimb being anal-ogous to the human knee, it can be extrapolated thatstifle surgeries may induce reflex inhibition of thequadriceps and surrounding muscles. Reflex inhi-bition of the human quadriceps occurs secondary toedema of the knee joint and joint capsule stretchreceptor responses, therefore making the musclesunresponsive to the neuromuscular efferent mes-sage to contract and furthering the disuse atrophy.Cutting or fenestration of the medial patellar liga-ment of the horse of which sartorius, gracilis, andquadriceps muscles tendons attach would certainlypropose the possibility that reflex inhibition mayfollow in the horse post-surgically and therefore,could provide some delay of the horses return tooptimal functional outcomes.

If a horse were to be stall-rested after MPD orfenestration, it would benefit from receiving the reg-imen outlined above to improve the outcome andprevent reflex inhibition and muscle disuse atrophycommonly associated with post-surgical prescribedstall rest. PT intervention with modalities and mo-tor-relearning exercises is ideal for promoting afaster return of functional mobility after caustic in-jections or surgery of MLD.

Limitations

My practice is not research-based; therefore, when Itreated these horses, I did not purposely set out tocollect data. Thus, much of what I have to reportand compare is based on assessment findings andtreatment outcomes of each horse’s scenario. Out-come measure varied for each subject. Many exter-nal variables limit the findings reported in this casereview. The most significant limitations in thisstudy are lack of objective measures and control ofvariables. In retrospect, when writing up this casereport, my sentiments follow the declaration by Roseet al.33: “Assessments that are conducted ‘in-field’can be limited by external variables and are difficultto perform with an appropriate level of repeatabil-ity.”33 The following two areas (lack of objectivemeasures and uncontrolled variable) followed by alist of areas to improve could benefit future methodsof data collection and better organization for a clin-ical trial of this program in the future.

Lack of Objective Measures

Strength is difficult to assess on a horse. Horsesare not applicable to perform manual muscle test-

ing. No strength assessment methods have beendeveloped regarding the horse. Circumferentialmeasures around the proximal pelvic limb or hindend have not been developed. Additionally, stan-dards of measures with specific landmark locationsand tools for measuring have not been established.The best method that one can postulate is to com-pare before and after photos, with controlled vari-ables of camera distance placement from horse,documented positions and distance lengths, and pos-sible width grid on background wall, to help assessmuscle hypertrophy. Because of the nature of theclients, their facilities, availability, and equipmentrestrictions, photo comparisons were not alwaysavailable. The most functional indicator ofstrength gains made by the horses that have under-gone this protocol is their ability to return to theirprior performance level (return to function). Otherindicators of improvement were decreased incidenceof IUFP symptoms reported by their owners. Sta-bility gains were determined by increased toleranceto carry out 10- to 20-s holds repeated 10–12 timesat LTP exercise.

Goniometric measurements of the stifle jointwhile standing in square would have been a benefi-cial objective measure for information regardingconformational significance. Also, measuring thestifle in the extreme of full flexion position wouldhave been helpful to prove flexibility gains. Mea-suring step lengths of hindlimbs before and afterapplication of this program could have provided in-formation regarding hamstring length changes.Rose et al.33 indicates that measuring stride lengthand ROM enables the findings to be directly appliedto equine performance.

Each horse presented as a different scenario withpositive but different findings for baseline establish-ment of IUFP. There is no established method ofrating the degree of severity for IUFP. Therefore,each horse’s starting and ending conditions arebased on subjective interpretation of symptom oc-currence. All horses had common symptoms ofIUFP with jumping patella, but some were moreaffected than others, with actual delayed release inwhich they would have to lift the limb up and out tothe side or sometimes kick out behind to loosen theirstifle from extension. All had history findings ofstumbling, tripping, getting caught in gaits, or giv-ing way of limbs.

Each client had their own objectives of what theywere looking for with their horses. Therefore, ter-mination of program may have occurred regardingwhat each individual owner wished to establishrather than achievement of a standard baseline cri-teria that this therapist would have preferred.A standard baseline for discharge criteria has notbeen established to date.

Uncontrolled Variables

Each horse presented as a different scenario pre-senting with different findings for baseline initiation





to the program. Many had pre-existing conditionsand a variety of diagnoses. Generalized outcomesare difficult to quantify and qualify because of thisreason of varied starting conditions of the involvedequines (uncontrolled variable) and various clientdecisions to terminate treatment.

Owners were a significant variable in the successof this program based on how much money theycared to spend, what their goals of success were, howmuch they pursued direct PT input, and how willingthey were to spend the required time to carry outthis labor-intensive program. Some owners werededicated to this program and made great gainswith their horses. Others were not as dedicated fora variety of reasons and thus, got lesser responsesfrom their horse. Often, after owners got comfort-able with the program and the horse started to showpositive gains, owners stopped requesting the PT tobe present. Direct treatment durations varied be-tween horses. Owners were instructed to continuewith rehab regimen in anticipation of regaining allmusculature return within 6 mo. Optimally, itwould have been ideal to have continued contactwith each horse’s progress for a 6-mo period to viewregained symmetry of muscle mass resolution of allIUFP symptoms. Often, economics were stated asa reason for discontinuing direct PT treatment.

Winter in New England is its own challenge. Du-moulin et al.7 noted that young horses and ponieswere mostly affected during winter months.7 Thesame is true in this author’s experience. Manyhorse owners have their horses stabled in theirbackyards without the advantage of indoor ridingarenas to keep horses in work. Therefore, manyNew England horses have the winter off. Manymay have access to large paddocks, but withoutgrass pasture to entice them and large accumula-tions of snow height, many horses opt to just standat run-in sheds or close to the food source of thebarn. Even horses that are housed at indoor arenafacilities are reduced in their turnout and exercisetime in winter. Significant cold temperatures andpoor weather decrease owner’s frequency of barnvisits and riding time. Hill accessibility use is re-duced second to all these reasons.

This author’s experience with problematic stiflehorses has involved primarily pleasure or dressagedisciplines but only one jumper. At this prelimi-nary time of this author’s experience, it could be justcoincidence. Hypothetically, these findings couldbe based on the fact that strength requirement forjumping heightens demands on the hind-end musclesystem to keep stifle musculature in prime condi-tion, and therefore, fewer jumpers are afflicted withIUFP. Jumpers work their hind-end enginesharder at power production by frequently puttingtheir pelvic limbs into a flexed (shortened) pre-jumpposition, exerting isotonic and plyometric39 musclepropulsion, and requiring significant strength ofhind-end musculature. This kind of activity maymaintain adequate neuromuscular input to keep pa-

tella-femoral biomechanics intact, which is what theactivity of squatting exercises does for the humanknee.

9. Where to Go From Here?

There is still much to determine regarding the ther-apeutic benefits of this stifle and pelvic limb-strengthening protocol. Ideally, this author wouldlike the opportunity to run a controlled study of thisprogram on a large group of horses under controlledcircumstances to test the validity of this approach.The idea of chondromalicia not being readily identi-fied in the horse16 and the theory that an overactivevastus medialis obliqous51 may contribute to theproblem of IUFP are areas that warrant more re-search. Several baseline scales need to be devel-oped, such as IUFP severity and strength-ratingscale, and establishing a discharge criteria couldcontribute positively in the clarification of establish-ing baselines for quantitative measures of improve-ment of IUFP.

For example, the measuring of muscle bulk deficitshould be developed for better determination if thisprogram increases muscle bulk in correlation ofstrength. The stifle is a difficult joint to measurefor circumference because of deep landmarks sub-merged within heavy surrounding muscles, makingit difficult to palpate on the horse. Therefore, mus-cle atrophy was judged on a subjective visible obser-vation rather than an objectively measuredcircumference, which would have been indicative ofmuscle hypertrophy. Another way to measure thisatrophy would have been by total circumferentialmeasurement around the horse’s entire hind end inthe horizontal plane at the level of the stifle joint,coursing the areas of quadriceps and bicep femorismuscles and encompassing the entire width of theback end. This measurement would have to bedone very specifically to keep measuring consistent.Lack of established protruding landmarks promotesgreater intra- and interrater error. Therefore, cur-rently, muscle strength can only be assessed interms of muscle bulk, endurance, and functionalbiomechanical performance, such as how manytimes the patella fixates within a set distance.

Based on the above research evidence, there arethree areas for improvement in terms of therapeuticinterventions to this program. First is the additionof use of electrotherapy modalities of TENS andE-stim. Use of electrical stimulation has been well-supported for pain and edema reduction, disinhibi-tion of arthrogenic muscle inhibition,24 andrecruitment of a greater number of motor units dur-ing contractions to build strength. Second, con-sider changing the frequency of the currentstretching protocol. The 2009 study by Rose et al.33

of stretching suggests that stretching every day maynot be appropriate for the horse but that stretching3 days/wk may provide some benefit in terms ofrange of movement.33 Third, incorporate joint mo-bilizations to pelvic limb joints for pain reduction.





The use of joint mobilization is shown to decreasepain52 in the human literature. Although not easyto visualize, the development of stifle joint and pa-tellar mobilizations may be beneficial to the horsewith stifle dysfunction treatment. Additional de-velopment of manual intervention and application ofstifle joint mobilization may be worthy consider-ations in equine study.

There is a significant deficit in the public aware-ness of PT interventions and approaches that cancompliment veterinary practices in treatment ofhorses with not only stifle dysfunction but also,other problems such as back pain and delayed soft-tissue healing. Increasing public education aware-ness to veterinarians and horse owners regardingPT availability has merit in the resolution of stifledysfunction and pelvic limb weakness in this cur-rent equine environment. In small-animal veteri-nary practices, many PTs are employed directly inthe clinical setting alongside the veterinary sur-geons and veterinary technicians. In the humanpractice, orthopedic surgeons work with PTs collab-oratively for better patient outcomes and reductionof economic expenditure. Surgeons prescribe PT tosurgical candidates before and as mandatory aftermany musculoskeletal surgeries. PT can often im-prove many ailments that stem from muscle weak-ness and poor flexibility that result in biomechanicalfaults, such as in the case of some IUFP situations,that may prevent horses from more invasive surger-ies. Post-surgically, PT can stimulate healing forfaster recoveries.

10. Conclusion

Many horses struggle with stifle dysfunc-tion. There is a wide variety of reasons for theseproblems. The most common of these reasons ismuscle weakness because of injury, surgery, immo-bility, or disease. The best approach for addressingthis debilitating condition of muscle weakness of thepelvic leg is to use an interdisciplinary team ofequine practitioners. The PT plays a pivotal rolewithin the team as a rehabilitation expert, providingthe optimal treatment of therapeutic strengtheningexercise program for a horse’s recovery from biome-chanical stifle dysfunction. The most rewardingaspect of PT is helping clients to help their horsesregain their pre-injury health status and return tofunction. In the case of the equine, this resultmeans that both the owner and practitioners in-volved feel confident in the horse’s wellbeing in theabsence of distress, pain, or dysfunction, allowingthe owner to confidently ride/work the horse forpleasure or competition.

Strengthening programs for stifle dysfunctionsuch as this program should start slowly with iso-metric exercises, similar to a human knee patient’sstart in rehab, to avoid pain and additional jointtrauma. Stifle problems require an aggressivecross-training approach of progressive strengthen-ing and stretching exercises, inclusive of hill work,

up and down, ground poles, long lining, and cavelet-ties, etc. Progression of the stifle program is de-manding on the horse as well as the owner, becausedaily intervention is needed for successful outcomes.

PT has much to offer the creatures of the animalkingdom. There is a need for more evidence-basedpractice in the world of animal PT. By developingthe field of animal rehabilitation, presentation ofincreasing research should support the approachesused for healing humans to be applied to animals,such as the approach in this stifle program. PTsneed to incorporate the translation of evidence intothe clinical practice of animal patient management.Crusading PTs that are practicing on animals needto continue to follow the human clinicians in therealm of developing clinical practice guidelines formanagement of all common animal pathologies tomake the profession of PT a substantial contributionto the world of animal health and rehabilitation.Animals get hurt and have the potential to heal aswell as humans. Treating them to promote theiroptimal recovery free of recurrence, chronic pain,disability, and possible demise is the goal. There ismuch to offer horses with stifle dysfunction in termsof non-invasive PT, such as this therapeuticstrengthening program.

11. Summary: Take Home Message

Horses with stifle dysfunction symptoms of IUFPcan be treated with PT approaches similar to theapproach by which humans are treated for recoveryof PFPS. Humans and horses with these maladiesshare faulty patellar-femoral biomechanics oftenstemming from muscle atrophy, decreased flexibil-ity, and poor neuromuscular responses. Treatmentof both IUFP and PFPS involves client education,increase in activity level, a stretching program, andan ascending therapeutic strengthening exerciseprogression.

A thorough veterinary examination should firstclear the horse for PT treatment referral. Horsesrecovering from injuries, surgery, or systemic dis-eases are appropriate for this program. This pro-gram is owner- and horse-intensive in terms of timeand energy for successful outcomes. The use of mo-dalities can be advantageous to promote healing,decrease pain, and decrease swelling responsethroughout the program. A variety of training aidsand therapeutic devices can contribute to exerciseprogram success. After the equine is symptom-free, a cross-training maintenance program shouldbe used to prevent recurrence.

Stifle dysfunction is a serious problem that, if leftuntreated, can lead to additional joint degradation.Professional intervention should start with veteri-narian evaluation and diagnosis. Provision of a PTintervention such as this program can now offerveterinarians and horse owners a specific protocol tofollow to avoid use of the common unspecified in-struction of work in straight lines and hill climbing.A more humane method of starting the horse on





pain-free exercises such as isometrics can be initi-ated for preliminary muscle strengthening followedby specific ascending exercises introduced in thisprogram. Variables of surface variety, hill inclina-tion, and jumping obstacles are recommended forcross-training and maintenance purposes. Con-sider equine PT in conjunction with veterinary med-icine approaches for optimal outcomes after injuryor during recovery from systemic diseases andsurgeries.

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aTheraband, Pro Therapy Supplies, Norcross, GA 30071.bKinesio-Tape, Pro Therapy Supplies, Norcross, GA 30071.





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