tratamiento no convencional de artrosis

Knee osteoarthritis (OA) is one ofthe most common causes of dis-ability. Persons with knee pain re-sulting from OA often cannot per-form activities of daily living,work, and sports.

Knee OA increases in prevalencewith advancing age. About 10% ofpersons older than 65 years havesymptomatic knee OA; during a 1-year period, about 25% of personsolder than 55 years have knee painon most days in a month.1 Thenumber of Americans older than65 years is expected to roughlydouble in the next 25 years, andthe challenge to providers of mus-culoskeletal care probably will in-crease accordingly.

Symptomatic knee OA develops

in many persons in their 40s and50s. Risk factors include obesity,occupational bending and lifting,knee injury, and previous surgery.The risk of knee OA is significantlyincreased in patients who have hada total meniscectomy.2 With the ad-vent of more conservative menis-cus-sparing surgery, total menis-cectomies rarely are performed,but even partial meniscectomymay increase the risk of knee OA.3

In addition, major ligamentousinjuries,such as a torn anterior cru-ciate ligament (ACL), predisposepersons to knee OA. Many youngerpatients currently seen in kneearthritis clinics have a history of ei-ther meniscal or ACL injuries.Thesepatients often are interested inmaintaining some lifetime sportsactivities, such as tennis, golf, cy-cling, softball, and walking for fit-ness.Usually, they are motivated toavoid or delay joint replacementsurgery. As a result, these patients

are excellent candidates for an ag-gressive nonpharmacologic, non-surgical approach to treatment.

Many therapies for knee OAhave been proved to be effective,but to help patients achieve a highquality of life the physician mustconsider biomechanical interven-tions—rather than rely solely onmedications or surgery—and thepatient must be willing to workhard. Physicians and physicaltherapists often find working withpatients to optimize the benefits ofthese potentially valuable inter-ventions very rewarding.

In this 2-part article, we de-scribe several nonsurgical, non-pharmacologic therapies for kneeOA. This first part highlights theimportant role that knee bracing,foot orthoses, and weight loss mayplay. In the second part, to appearin a later issue of this journal, wewill focus on exercise and fitnessfor knee OA treatment.

Patients often want to maintain sports activities and avoid surgery

Nonpharmacologic, nonsurgical management of knee osteoarthritisABSTRACT: Greater load in the medial compartment of the knee thanin the lateral compartment may contribute to knee osteoarthritis (OA).Malalignment also has been associated with the progression of radio-graphic joint-space loss and loss of function. Treatment involves re-ducing the load to reduce knee pain and improve function. Osteot-omies are technically demanding and associated with morbidity.Knee bracing may correct malalignment, reduce the load, reduce thevarus moment, increase proprioception, and stabilize an unstableknee. Foot orthoses have been shown to reduce the symptoms of medi-al compartment knee OA. Weight loss in combination with exercise re-duces pain and improves physical function. Many persons with kneeOA experience instability problems; bracing and exercise may help im-prove them. (J Musculoskel Med. 2006;23:430-443)

430 THE JOURNAL OF MUSCULOSKELETAL MEDICINE • JUNE 2006

KELLY KROHN, MDG. KELLEY FITZGERALD, PT, PhD

Dr Krohn is director of clinical research atMercy Hospital of Pittsburgh. Dr Fitzgeraldis associate professor in the department of physical therapy at the University ofPittsburgh.

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Load and malalignmentLoad across the knee is not uni-formly distributed during normalgait. The medial compartment ex-periences load greater than that ofthe lateral compartment. This im-balance may contribute to thestart of OA and lead to narrowingof the joint space in the medialcompartment, an early sign of OA(Figure 1).

During the midstance phase ofgait, an estimated 60% to 80% ofthe load is distributed to the me-dial compartment of a normalknee. This is explained by the ex-ternal varus moment (or adductormoment), the torque generatedfrom the ground reaction forceduring the stance phase that re-sults from the body’s center ofgravity falling medial of the kneejoint. This uneven distribution, inpart, is why medial compartmentOA is more prevalent than lateralcompartment disease.

Malalignment also has been as-sociated with the progression ofradiographic joint-space loss anddeterioration in function in pa-tients with knee OA. Varus align-ment increases the risk of medialcompartment OA progression; val-gus alignment increases the risk oflateral compartment OA progres-sion.4 In a patient who has medialcompartment knee OA with sig-nificant cartilage loss or varusmalalignment or both, the per-centage of the load that is distrib-uted to the medial compartmentduring the midstance phase of gaitmay be much higher than 80%.

Correction of malalignment and reduction of loadBy understanding normal kneebiomechanics and the impact of

malalignment on knee OA, clini-cians may increase the therapeuticoptions for patients who havesymptomatic unicompartmentalknee OA beyond the usual medi-cations, injections, and surgery.The strategy is to reduce the loadon the symptomatic compartmentto reduce knee pain and improvefunction.

Historically, osteotomies of theproximal tibia or distal femur havebeen performed to improve mal-

alignment and reduce the load onthe affected compartment. Theseprocedures are technically demand-ing and associated with knownmorbidities, such as infection,nerve injury, deep venous throm-bosis, and malunion/nonunion;also, risks are inherent in admin-istration of anesthesia. If the pa-tient eventually has total kneearthroplasty, the surgery may bemore difficult than that performedin a knee that has not previously un-

THE JOURNAL OF MUSCULOSKELETAL MEDICINE • JUNE 2006 431

Spiking of the tibial eminence

Sclerosing ofarticular surfaces

Medial compartmentjoint-spacenarrowing

Marginalosteophytes

Figure 1 – Narrowing of the joint space in the medial compartment of the kneeis an early sign of osteoarthritis (OA). Bony sclerosis and formation of spikes onthe tibial eminence and osteophytes also may become apparent. Medial joint-space narrowing with tibial osteophyte formation consistent with medial com-partment knee OA is seen in this x-ray film (inset).

Illustration © Robert M

argulies, CM

I 2006

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dergone osteotomy. Nonsurgical al-ternatives for improving malalign-ment and reducing the load on theaffected compartment include kneebracing and foot orthoses.

The benefits of bracingKnee bracing has become an ac-cepted intervention for patientswith knee OA. The potential bene-fits include correction of malalign-

ment, reduction of the load acrossthe involved compartment, reduc-tion of the varus moment, in-creased proprioception, stabiliza-tion of an unstable knee, and increased patient perception ofstability (Table).

Some patients with knee OAhave true ligamentous instability,such as a torn ACL. Many patientshave pseudolaxity that resultedfrom loss of articular cartilage andreduced muscle tone. With theirrigid shells and hinge systems,well-fit knee OA braces providepatients with increased stability.

A key characteristic of the kneeOA brace is its ability to create avalgus or varus force on the limb


Table – Potential benefits of knee bracing for knee OA

•Correction of malalignment•Reduction of the biomechanical load on the diseased knee compartment•Increased mechanical stability in an unstable knee with ligamentous injury•Increased mechanical stability in a knee with pseudolaxity•Increased proprioception•Increased patient perception of knee stability•Placebo effect

OA, osteoarthritis.

Nonpharmacologic,nonsurgical management of knee osteoarthritis

Figure 2 – Braces used for knee osteoarthritis (OA) help create a valgus or varus force on the limb to reduce the load on theinvolved knee joint compartment. Several brace designs for right knee medial compartment OA are shown here. Specificbraces may have different hinges, shells, padding, straps, and angle adjustments. Having a variety of designs to choosefrom helps physicians match a design to a specific patient’s needs. Companies that make models for the various designsare listed above each brace type.

Double uprightBregDonJoyInnovation Sports (Ossur)OMNI Life ScienceTownsend Design

Single upright withstrapDonJoyGeneration II (Ossur)

Single uprightBledsoeOMNI Life ScienceSeattle SystemsTownsend Design

Cloth-based sleevewith hingeBauerfeindDonJoy

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to reduce the load on the involvedknee joint compartment. This canbe accomplished with severalbrace designs, including a doubleupright system, single uprightsystem, single upright systemwith a contralateral strap, andcloth-based sleeves with hingesembedded (Figure 2).

Many features of a specificbrace are unique to the manufac-turer and protected by patent law.These features include the hingedesign, adjustability of the brace’sangle, shell materials, and strap-ping mechanisms.

Having a growing variety ofavailable OA brace designs is a bigadvantage: a design may be chosenthat best suits a patient’s kneepathology, leg size (thigh and calfgirth), vanity, and desired activi-ties. For example, a patient whohas true ACL deficiency may bene-fit from a more rigid double up-right knee brace design that isquite similar in design to the typ-ical functional ACL brace. An old-er woman with limited musclemass may prefer a low-profilecloth-based brace that has littlebiomechanical stability/leverage.

Knee brace clinical trials are dif-ficult to control adequately be-cause obtaining a true controlgroup presents challenges. In thelargest clinical trial to date (119patients with medial compart-ment knee OA in 3 treatmentgroups), symptoms and functionimproved more in the group with avalgus knee brace than in placeboand neoprene sleeve groups.5

Gait laboratory studies haveshown improved symmetry in gaitin patients who are wearing a val-gus knee brace.6 Digital radio-graphic studies of the gait cycle

have shown nicely that it is possi-ble to demonstrate increased me-dial joint space during midstanceand heel strike in patients who areusing a single upright valgusbrace compared with identical radiographs taken without thebrace.7

Many improvements have beenseen in the materials and design ofknee braces during the past de-cade. Knee OA braces currently on

the market may have distinct ad-vantages for various patient pop-ulations. In many of the braces, theangle of the hinge or the hinge at-tachment can be adjusted to theshell of the thigh or calf. This al-lows the physician and orthotist todial in a dose effect for an individ-ual brace.

Fitting of the brace and instruc-tions on how to don it properly arecrucial for success. The orthotist,a key member of the team, must befamiliar with the nuances of sev-eral varieties of knee braces to al-low the clinician some flexibilityin using different braces for dif-ferent patients.

A helpful office evaluation ma-neuver used to determine whetherthe patient might benefit from abrace is applying a valgus or varusforce to the patient’s leg (Figure 3).The physician’s hand is used as afulcrum at the joint with the pa-tient’s knee slightly flexed. If avarus or valgus knee can be re-duced to near neutral easily withthis simple maneuver, there is areasonable chance that a properlyfit and adjusted knee brace canimprove the malalignment.

Another office screening methodfor prescribing a knee brace is tohave some sample braces in the of-fice and allow the patient to holdthe brace. If the patient is not in-terested in trying the brace afterholding it, he or she probably willnever wear it.

Custom knee braces may costbetween $800 and $1800. Off-the-shelf models are less expensivebut may have limitations in fittingor compromise quality, such as inthe hinge or shell materials. Kneebraces are only for a niche withinthe large population of patients



Figure 3 – Applying a valgus force tothe patient’s leg helps determinewhether the patient might benefitfrom wearing a brace.Using one handas the fulcrum with the patient’s kneeflexed about 10° to 15°, the clinicianmay apply a force to see whether themalalignment can be reduced. Allow-ing the patient to hold a brace is an-other helpful office screening method.

(continued from page 432)

0606JMMKrohn 7/26/06 4:30 PM 41

with knee OA, but when use ofthem is successful, patients oftenaccept them and are able to returnto some of their lifetime sports orwork activities (Figure 4).

If a patient has a good clinicalresponse, with decreased pain andincreased ability to perform activ-ities, he often will wear a knee OAbrace for many years. Some of ourpatients have worn braces formore than 10 years; other patientswear knee braces for a few yearsand then consider surgical inter-vention. With the advent of newlighter-weight and more comfort-able braces, long-term adherencemay be enhanced.

Foot orthosis optionsLateral heel wedges and lateralwedge foot orthoses have beenshown to reduce the symptoms ofmedial compartment knee OA.8

Biomechanical studies have dem-onstrated that both the externalvarus moment and the estimatedmedial compartment load of theknee are reduced with lateralwedge orthoses.

There appears to be a dose re-sponse with the degree of lateralwedging.However, the benefits of ahigher degree of wedging are limit-ed by foot and ankle discomfort. Areasonable amount of lateral wedg-ing for medial compartment kneeOA appears to be about 4° to 6°.

Custom foot orthoses may bebeneficial in patients with footand ankle abnormalities; howev-er, a simple off-the-shelf lateralwedge orthosis may suffice for pa-tients who have medial compart-ment knee OA and a basically nor-mal foot and ankle. Although theresults from clinical trials con-ducted to validate the benefit of

foot orthoses for knee OA havebeen mixed, these devices providea low-cost, safe intervention thatmerits an empiric trial in manypatients.

The value of weight lossObesity is well established as arisk factor for knee OA. Studieshave clearly shown that weight

loss in combination with exercisereduces pain and improves physi-cal function in patients with kneeOA.9 Clinicians may encourageweight loss in patients with symp-tomatic knee OA by sharing thefollowing concept:

A load of 3 to 5 times a person’sbody weight is transmitted acrossthe knee joint during walking (andthis load is significantly higherduring running). Therefore, a de-crease in weight of 10 lb can de-crease the load across the kneejoint by 30 to 50 lb.

Instability in personswith knee OAA significant proportion of per-sons with knee OA experienceproblems with knee instability. Ina recent study, Fitzgerald and as-sociates10 reported the prevalenceof self-reported knee instability(defined as a sensation of buck-ling, shifting, or “giving way”at theknee during functional activities)and its relationship with physicalfunction.

More than 60% of study patientsreported episodes of instability,and 44% indicated that knee insta-bility affected their ability to per-form activities of daily living. Theseverity of knee instability was as-sociated with poorer functionalperformance, even after control-ling for other factors that could af-fect function in persons with kneeOA,such as pain,muscle weakness,and reduced joint mobility.The au-thors concluded that knee insta-bility is a prevalent problem inpersons with knee OA and that itcontributes to disability above andbeyond what may be expected fromthe presence of other impairments.

The instability experienced by



Figure 4 – When wearing of braces issuccessful, patients with osteoarthri-tis often can return to lifetime sportsor work activities.

Weight loss in combination withexercise reduces

pain and improvesphysical function inpatients with knee

osteoarthritis.

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persons with knee OA probably ismultifactorial; it may result fromincreased capsuloligamentous lax-ity, structural damage to the knee,and altered muscular strength andneuromuscular control. Investiga-tors have reported increased pas-sive knee laxity in persons withknee OA.

The laxity has been described asa “pseudolaxity.” Although capsu-loligamentous structures remainintact, the laxity is thought to re-sult from reduced tension in thejoint capsule and ligaments sec-ondary to progressive degenera-tive changes in the joint and in-creased joint-space narrowing.11

The passive restraints arethought to slacken as the diseaseprocess progresses. Sharma andcolleagues12 reported that greateramounts of passive varus/valguslaxity are associated with greateramounts of bony attrition andjoint-space narrowing of the knee,providing some support for the no-tion of pseudolaxity.

Evidence is mounting to indi-cate that knee instability and in-

creased laxity may influence phys-ical function and motor controlpatterns of the lower extremity.Given that knee instability maycontribute to the decline of physi-cal function above and beyondthat which may be explained byother impairments (eg, loss of jointmotion, muscular weakness, andpain), simply addressing range ofmotion, pain, and muscular weak-ness in exercise programs may notbe enough to overcome problemswith knee instability.

Adjunctive interventions that

have been used to address insta-bility in other patient populations,such as knee bracing and agilityand perturbation training, may beneeded in conjunction with gener-al exercise programs to resolve instability problems. Further re-search is needed to determine howknee instability and laxity may in-fluence the outcome of rehabilita-tion and whether adjunctive treat-ments that directly address kneeinstability can improve the overalleffect of exercise therapy for per-sons with knee OA. ■

1. Peat G, McCarney R, Croft P. Knee pain andosteoarthritis in older adults: a review of com-munity burden and current use of primaryhealth care. Ann Rheum Dis. 2001;60:89-90.2. Roos H, Lauren M, Adalberth T, et al. Kneeosteoarthritis after meniscectomy: prevalence ofradiographic changes after twenty-one years,compared with matched controls. ArthritisRheum. 1998;41:687-693.3. Englund M, Roos EM, Lohmander LS. Impactof type of meniscus tear on radiographic andsymptomatic knee osteoarthritis: a sixteen-yearfollowup of meniscectomy with matched con-trols. Arthritis Rheum. 2003;48:2178-2187.4. Cerejo R, Dunlop DD, Cahue S, et al. The in-fluence of alignment on the risk of knee os-teoarthritis progression according to baseline

stage of disease. Arthritis Rheum. 2002;46:2632-2636.5. Kirkley A, Webster-Bogaert S, Litchfield R, etal. The effect of bracing on varus gonarthrosis.J Bone Joint Surg. 1999;81A:539-548.6. Draper ER, Cable JM, Sanchez-Ballester J, etal. Improvement in function after valgus brac-ing of the knee: an analysis of gait symmetry. J Bone Joint Surg. 2000;82B:1001-1005.7. Komistek RD, Dennis DA, Northcut EJ, et al.An in vivo analysis of the effectiveness of the os-teoarthritis knee brace during heel-strike of gait.J Arthroplasty. 1999;14:738-742.8. Marks R, Penton L. Are foot orthotics effica-cious for treating painful medial compartmentknee osteoarthritis? A review of the literature.Int J Clin Pract. 2004;58:49-57.

9. Messier SP, Loeser RF, Miller GD, et al.Exercise and dietary weight loss in overweightand obese older adults with knee osteoarthritis:the Arthritis, Diet and Activity Promotion Trial.Arthritis Rheum. 2004;50:1501-1510.10. Fitzgerald GK, Piva SR, Irrgang JJ. Reports ofjoint instability in knee osteoarthritis: its preva-lence and relationship to physical function.Arthritis Rheum. 2004;51:941-946.11. Sharma L, Lou C, Felson DT, et al. Laxity in healthy and osteoarthritic knees. ArthritisRheum. 1999;42:861-870.12. Sharma L, Cahue S, Song J, et al. Physicalfunctioning over three years in knee osteo-arthritis: role of psychosocial, local mechanical,and neuromuscular factors. Arthritis Rheum.2003;48:3359-3370.

Practice Points■ In patients with knee osteoarthritis (OA), improving malalignment andreducing the load on the symptomatic knee joint compartment helps re-duce pain and improve function.■ Applying a valgus or varus force to the patient’s leg may help deter-mine whether the patient might benefit from a brace. Allowing the pa-tient to hold a sample brace helps determine whether the patient willwear it.■ Foot orthoses have been shown to reduce the symptoms of medialcompartment knee OA. There appears to be a dose response with the de-gree of lateral wedging.

References

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As a result of knee osteoarthritis(OA),patients often cannot performactivities of daily living, work, andsports.Many patients would like tomaintain some level of sports ac-tivity but want to avoid or delayjoint replacement surgery. Non-pharmacologic, nonsurgical ap-proaches provide other optionsthat may help them in their questfor a higher quality of life.

Numerous studies have demon-strated that exercise and physicalactivity programs provide effec-tive treatment for persons whohave knee OA.1 Most programs in-clude muscle strengthening, flexi-bility, and aerobic exercises. Al-though these programs have beenfound to be beneficial in reducingpain and improving function, their

overall effect has been limited tomoderate at best.2,3

One possible reason is that tra-ditional approaches to exercise forpatients with knee OA have beengeneralized. There is a consider-able amount of variability in pa-tients’ physical capacity and indi-vidual characteristics (eg, obesity,lower extremity alignment, kneeinstability, structural damage,pain tolerance, fear, and anxiety)that may account for differences intheir responsiveness to exercise.4

Recent evidence suggests that tai-loring exercise programs to moreclosely fit each patient’s specificneeds may improve the treatmentresults.5

In this 2-part article, we discussvarious nonsurgical, nonpharma-cologic therapies for patients withknee OA.The first part (“Nonphar-macologic, nonsurgical manage-ment of knee osteoarthritis,” TheJournal of Musculoskeletal Med-icine, June 2006, page 430) de-

scribed the important role thatknee bracing, foot orthoses, andweight loss may play. In this sec-ond part, we feature exercise andfitness for knee OA treatment. Wediscuss the key elements of an ex-ercise program and factors thatmay help enhance its overall effec-tiveness in improving patients’physical function.

MUSCLE STRENGTHENINGEXERCISESStrengthening of the lower ex-tremity muscles is an importantcomponent of an exercise programfor persons with knee OA. Muscleweakness has been shown to beassociated with greater levels ofdisability in patients with kneeOA6-8; some investigators have ar-gued that muscle weakness maybe a precursor to knee OA.9,10 In ad-dition, because muscles may playa significant role in absorbing anddissipating loads across the joints,maintaining adequate strength

Tailoring programs to fit each patient’s specific needs may improve results

Exercise for managementof knee osteoarthritisABSTRACT: Exercise and physical activity programs have beenshown to reduce pain and improve function in patients with kneeosteoarthritis (OA). However, their overall effect may have been lim-ited by lack of tailoring to fit each patient’s specific needs. Both iso-metric and isotonic exercises have been used effectively to strength-en the lower extremity muscles. Open chain and closed chainexercises may be used, depending on a specific patient’s goal.Strengthening of hip and ankle muscles should be addressed. Thekey to a flexibility and mobility program is to address limitations inall lower extremity joints. There is growing interest in the use of balance and agility training activities in knee OA exercise pro-grams. (J Musculoskel Med. 2006;23:505-509)

THE JOURNAL OF MUSCULOSKELETAL MEDICINE • JULY 2006 505

KELLY KROHN, MDG. KELLEY FITZGERALD, PT, PhD

Dr Krohn is director of clinical research atMercy Hospital of Pittsburgh. Dr Fitzgeraldis associate professor in the department of physical therapy at the University ofPittsburgh.

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Exercise for managementof knee osteoarthritis

and fitness of the lower extremitymuscles is an important compo-nent of rehabilitation.

A variety of methods may beused for lower extremity strengthtraining in knee OA rehabilitationprograms. Both isometric exercis-es (muscular force is exertedagainst a static resistance) andisotonic exercises (muscle con-traction is resisted through arange of motion of the target joint)have been used effectively.5,6,11,12

Many patients can tolerate iso-tonic exercises without difficulty.However, shear forces that are cre-ated when resistance is appliedduring joint motion may repro-duce symptoms in some patientswith knee OA. Isometric exercisesoffer an effective alternative forthese patients, because relativelyhigh resistance loads can be toler-

ated without exposing the joint tohigh shear forces.

Types of strengthening exercisesAnother factor to consider in mus-cular strength training programsis the use of open chain or closedchain exercises. Typically, openchain exercises are non–weight-bearing exercises in which themovement occurs mostly at 1 jointand resistance to a single musclegroup is emphasized (eg, a leg ex-tension exercise for quadricepsstrengthening or a leg curl exer-cise for hamstring strengthening)(Figure 1). Closed chain exercisesusually are weight-bearing exer-cises in which movement occurs atseveral joints and resistance is ap-plied to several muscle groups (eg,squatting or leg press exercises)

(Figure 2). During closed chain ex-ercises, movement must occur atthe hip, knee, and ankle to com-plete the task and the hip exten-sors, knee extensors, and ankleplantar flexors all are involved in overcoming or controlling theresistance.

Both open chain and closedchain exercises may be used in re-habilitation. If the goal is to targeta specific muscle group to improveforce output capabilities, openchain exercises may be more effec-tive. If the goal is to encourage co-ordinated use of multiple lowerextremity muscle groups, closedchain exercises would be used. Pa-tients who cannot bear weight be-cause of pain may be more suc-cessful with open chain exercises;other patients may not toleratesome open chain exercises but are

Figure 1 – Open chain and closed chain exercises may be used in muscular strength training programs for patients withknee osteoarthritis. Open chain exercises usually are non–weight-bearing exercises in which the movement occurs most-ly at 1 joint. A leg extension exercise for quadriceps strengthening is shown with the leg in extension at 90° of knee flex-ion (start position, A) and the leg in extension at 45° of knee flexion (end position, B).

BA

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able to perform closed chain exer-cises without difficulty.

Another factor to consider is thearc of motion through which openchain and closed chain exercisesare performed. Patellofemoraljoint stress may be systematicallyincreased when an open chain legextension exercise is performedfrom 90° of flexion to full exten-sion. In contrast, patellofemoraljoint stress is systematically in-creased during a closed chain legpress exercise from full extensionto 90° of flexion.

Patellofemoral joint stress can beminimized during both of these ex-ercises if the arcs of motion arelimited to the ranges in which thereis less joint stress. For open chainleg extensions,patellofemoral jointstress is minimized from 90° to 45°of flexion (see Figure 1).The closedchain squat and leg press exercisescan be performed with minimaljoint stress from full extension toabout 45° of flexion (see Figure 2).

There is evidence to indicate thatopen chain leg extension exercisesalso may increase anterior tibialtranslation and, therefore, increaseanterior shear forces when the legis extended from about 60° of flex-ion to full extension in patientswith anterior cruciate ligament de-ficient–knees.13,14 Anterior transla-tion may be reduced in these pa-tients during open chain leg exten-sions by limiting the arc of motionto a range of 90° to 45° of flexion.

Although quadriceps strength-ening often is emphasized in aknee OA rehabilitation program,strengthening of hip and anklemuscles also should be addressed.Weakness of the hip abductor andexternal rotator muscles has beenassociated with various knee pa-

thologies, including knee OA.15,16

Poor motor control of the hip isthought to alter the stress on theknee during locomotion, placingknee structures at risk for injury.Weakness of ankle muscles hasbeen shown to be associated withbalance deficits in persons withknee OA.17 Techniques that focuson hip and ankle muscle strength-ening should be included in an ex-ercise program for these patients(Figure 3).

Intensity of strengthening exercisesAnother consideration in planninga strengthening program for per-sons with knee OA is the intensityof exercise.The amount of tensionproduced in the muscle during

training is a key factor in inducinga training effect. If the program isnot intense enough, it probablywill not be beneficial.

In studies that have reportedpositive results in improving mus-cle strength, progressive resis-tance that is tailored to the indi-vidual patient’s force-producingcapabilities was used.5,6,11,18 Oneapproach is to use a percentage ofthe patient’s maximum force pro-duction, starting the training loadat 10% of maximum and increas-ing it by 10% each week to 70% ofmaximum.6

Some investigators have used aresistance load that was equatedwith a moderately intense ratingon the Borg Perceived ExertionScale to tailor individual resis-

Figure 2 – Closed chain exercises generally are weight-bearing exercises.Movementmust occur at the hip, knee, and ankle, and several muscle groups help overcomeor control the resistance. Shown is a leg press with the knee at 45° of flexion (endposition).The start position is 0° of flexion.

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tance loads.11,18 As the Borg ratingdecreased for a given load, the re-sistance was then increased ac-cordingly. Others have describedthe training load as the maximumresistance that can be performedin 2 sets of 10 repetitions. Resis-tance is then increased as the patient is able to perform 2 sets of 12 repetitions in 3 consecutive sessions.12

In patients with knee OA, thedefinition of maximum also mayinclude the maximum amount of

resistance that can be lifted or re-sisted without reproducing jointpain symptoms. These maximumloads are then reestablished every1 or 2 weeks so that the trainingloads can be increased as the pa-tient improves.

FLEXIBILITY AND AEROBIC EXERCISESReduced joint motion may resultin a reduced area of joint load dis-tribution during locomotion; this,in turn, may increase joint stress.

Limitations in joint motion alsomay alter the patient’s ability toperform various functional tasks.Deyle and associates5 included a comprehensive flexibility andjoint mobilization program intheir study, which yielded greaterimprovements in pain and func-tion than previous studies. Flexi-bility exercises were performed onthe quadriceps, hamstring, gas-trocnemius, hip adductor, and hipflexor muscle groups, as well asthe iliotibial band. The key to theflexibility and mobility program,if greater gains in function are ex-pected, is to address limitations inall lower extremity joints and notjust in the knee.

Aerobic exercise has long beenshown to help improve functionand measures of cardiovascularfitness in older persons and inpersons with knee OA.12,19-21 Lowerimpact aerobic activities (eg, walk-ing, cycling, and aquatic aerobicexercises) performed at an inten-sity ranging from 60% to 75% ofmaximum heart rate for 30 to 45minutes, 3 to 5 days per week, al-so have been shown to be benefi-cial. These activities may providebenefit without exacerbating kneepain and inflammation. Aerobicexercise combined with a properdietary regimen also may help re-duce obesity, a major risk factorfor progression of knee OA.22

BALANCE AND AGILITY TRAININGThere is growing interest in theuse of balance and agility trainingactivities in knee OA exercise pro-grams. Techniques used to chal-lenge balance may include tandemwalking and wobble or tilt boardactivities.


(continued)

Figure 3 – Strengthen-ing of hip and anklemuscles should be ad-dressed in a knee os-teoarthritis rehabilita-tion program, becauseweakness of hip abduc-tor and external rotatormuscles has been asso-ciated with knee path-ologies and weakness ofankle muscles has beenshown to be associatedwith balance deficits.Thigh adductor (A),thigh abductor (B), andcalf curl (C) exercises areshown.

A B

C

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Agility training techniques em-phasize quick stops and starts,quick changes in direction, andobstacle negotiation. These typesof activities, which traditionallyhave been used for younger, phys-ically active persons, are beingmodified for use in exercise pro-grams for persons with knee OA.23

The rationale is that these activi-ties expose patients to higher-lev-el movement problems and chal-lenges to lower extremity stabilitythat typically are encounteredduring normal activities of dailyliving.

General flexibility, strengthen-

ing, and aerobic exercises alone do not provide this type of experi-ence. The addition of balance andagility training activities might

add to the benefit of these exercis-es by providing patients with anopportunity to learn how to solvemore complex movement tasks. ■


Practice Points■ In strengthening exercises for persons with knee osteoarthritis, openchain exercises target a specific lower extremity muscle group; closedchain exercises encourage coordinated use of multiple muscle groups.■ Flexibility exercises are used to improve pain and function. The key is toaddress limitations in all lower extremity joints, not just in the knee.■ Balance and agility training activities provide patients an opportunityto learn how to solve more complex movement tasks.

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osteoarthritis. Arthritis Rheum. 2004;51:40-48.9. Radin EL, Yang KH, Riegger C, et al. Rela-tionship between lower limb dynamics andknee joint pain. J Orthop Res. 1991;9:398-405.10. Slemenda C, Heilman DK, Brandt KD, et al.Reduced quadriceps strength relative to bodyweight: a risk factor for knee osteoarthritis inwomen? Arthritis Rheum. 1998;41:1951-1959.11. Topp R, Woolley S, Hornyak J 3rd, et al. Theeffect of dynamic versus isometric resistancetraining on pain and functioning among adultswith osteoarthritis of the knee. Arch Phys MedRehabil. 2002;83:1187-1195.12. Ettinger WH Jr, Burns R, Messier SP, et al. Arandomized trial comparing aerobic exerciseand resistance exercise with a health educationprogram in older adults with knee osteoarthri-tis. The Fitness Arthritis and Seniors Trial (FAST).JAMA. 1997;277:25-31.13. Yack HJ, Collins CE, Whieldon TJ. Com-parison of closed and open kinetic chain exer-cise in the anterior cruciate ligament-deficientknee. Am J Sports Med. 1993;21:49-54.14. Jenkins WL, Munns SW, Jayaraman G, et al.A measurement of anterior tibial displacementin the closed and open kinetic chain. J OrthopSports Phys Ther. 1997;25:49-56.15. Ireland ML, Willson JD, Ballantyne BT, DavisIM. Hip strength in females with and withoutpatellofemoral pain. J Orthop Sports Phys Ther.2003;33:671-676.16. Mascal CL, Landel R, Powers C. Man-agement of patellofemoral pain targeting hip,pelvis, and trunk muscle function: 2 case re-

ports. J Orthop Sports Phys Ther. 2003;33:647-660.17. Jadelis K, Miller ME, Ettinger WH Jr, MessierSP. Strength, balance, and the modifying effectsof obesity and knee pain: results from theObservational Arthritis Study in Seniors (OASIS).J Am Geriatr Soc. 2001;49:884-891.18. Baker KR, Nelson ME, Felson DT, et al. Theefficacy of home based progressive strengthtraining in older adults with knee osteoarthritis:a randomized controlled trial. J Rheumatol.2001;28:1655-1665.19. Kovar PA, Allegrante JP, MacKenzie CR, etal. Supervised fitness walking in patients withosteoarthritis of the knee: a randomized, con-trolled trial. Ann Intern Med. 1992;116:529-534.20. Morey MC, Cowper PA, Feussner JR, et al.Evaluation of a supervised exercise program ina geriatric population. J Am Geriatr Soc. 1989;37:348-354.21. Minor MA, Hewett JE, Webel RR, et al.Efficacy of physical conditioning exercise in pa-tients with rheumatoid arthritis and osteo-arthritis. Arthritis Rheum. 1989;32:1396-1405.22. Messier SP, Loeser RF, Miller GD, et al.Exercise and dietary weight loss in overweightand obese older adults with knee osteoarthritis:the Arthritis, Diet, and Activity Promotion Trial.Arthritis Rheum. 2004;50:1501-1510.23. Fitzgerald GK, Childs JD, Ridge TM, IrrgangJJ. Agility and perturbation training for a physi-cally active individual with knee osteoarthritis.Phys Ther. 2002;82:372-382.

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