REVIEW ARTICLE

Review: imaging of groin pain in the athlete

Alun G. Davies & Andrew W. Clarke & J. Gilmore &

M. Wotherspoon & David A. Connell

Received: 27 April 2009 /Revised: 28 June 2009 /Accepted: 17 July 2009 /Published online: 27 August 2009# ISS 2009

Abstract Chronic groin pain is a common entity in thesporting population and causes considerable morbidity. Thedifferential diagnosis is wide, and this article presents areview of the common causes with particular reference toanatomy, ultrasound and magnetic resonance imaging(MRI) findings.

Keywords Chronic groin pain . Groin injury . Sports hernia .

Athletic pubalgia . Adductor enthesopathy . Osteitis pubis .

Review

Introduction

Chronic groin pain is a common problem in professionalathletes and is reported to account for 2–5% of all sportsinjuries [1]. It is responsible for significant morbidity,leading to time away from training and competition andmight be a career-ending injury. Furthermore, if athletes areunable to return to sport, this problem might have adramatic economic impact on professional sporting clubsand organisations. The prevalence of groin pain variesamong different sports activities but is essentially commonin those involved in repeated kicking and rapid change ofdirection, such as soccer, tennis, football, and ice and fieldhockey. In these sports the incidence may rise to 5–7% ofall injuries [1].

In clinical practice the term athletic pubalgia is oftenused to describe exertional pubic or groin pain that mightbe secondary to a number of different pathologicalconditions (Table 1).

The anatomic and biomechanical considerations forgroin injuries are amongst the most complex in themusculoskeletal system. This makes clinical differentiationand subsequent management difficult, due to the consider-able overlap of symptoms and examination findings [2]. Inaddition, athletes may have one or more of these conditionsco-existing, making diagnosis and treatment problematic.The aim of this study was to review the regional anatomyof the groin, which is a prerequisite for understanding thepotential causes of athletic pubalgia. The imaging techni-ques that can be utilised are discussed, together withtechnical considerations for high-quality imaging. Weconcentrate on the pathology involving the symphysispubis and adjacent soft tissues, including osteitis pubis,adductor enthesopathy, symphyseal disc degeneration, thepre-hernia complex (sports hernia) and pubic stress frac-tures. Generalised causes of hip and pelvic pain are outsidethe remit of this article.

Regional anatomy

The pubic symphysis is a non-synovial, diarthrodial joint,formed between the two oval articular surfaces of themedial portion of the superior rami (Fig. 1). Each of theopposed surfaces of the pubic bones is covered by a thinlayer of hyaline cartilage firmly joined to the bone by aseries of processes, which accurately fit into thecorresponding depressions on the osseous surfaces. Theseopposed cartilaginous surfaces are connected together by anintermediate lamina of fibrocartilage, which varies in

A. G. Davies :A. W. Clarke (*) : J. Gilmore :M. Wotherspoon :D. A. ConnellDepartment of Radiology,Royal National Orthopaedic Hospital NHS Trust,Brockley Hill,Stanmore, Middlesex HA7 4LP, UKe-mail: andrew.clarke@rnoh.nhs.uk

Skeletal Radiol (2010) 39:629–644DOI 10.1007/s00256-009-0768-9

Table 1 Differential diagnosis of groin pain in athletes. Entities discussed in this review are in bold type

Structure Conditions causing groin pain

Symphysis pubis 1. Osteitis pubis

2. Adductor enthesopathy

3. Symphyseal disc degeneration

4. Stress fractures

Hernia 1. Sports hernia

2. Direct/indirect inguinal hernia

3. Femoral hernia

Hip joint 1. Hip labral tear

2. Snapping hip syndrome

a. Intra-articular cause

∙ Labral tear∙ Intra-articular loose body

∙ Synovial osteochondramatosis

b. Extra-articular cause

Internal (iliopsoas tendon)

External (ilio-femoral tendon)

Posterior (long head of biceps)

3. Osteoarthritis

4. Osteochondritis dissecans

5. Chondral injuries

6. Fractures

7. Subluxation

8. Slipped upper femoral epiphysis

Bursae 1. Trochanteric bursitis

2. Subgluteus medius bursitis

3. Iliopsoas bursitis

Muscle strain/tear/contusion 1. Rectus abdominis asymmetry/tears

2. Adductor muscles

3. Quadriceps muscles

4. Hamstring muscles

5. Iliopsoas muscle

Spine (referred pain) 1. Lumbar spondylosis

2. Transitional anatomy at the lumbosacral junction

3. Facet joint abnormalities

4. Erector spinae abnormalities

Pelvic pathology in youngfemale athletes

1. Ovarian pathology

2. Endometriosis

3. Adenomyosis

Neuropathy 1. Pudendal and genital branch of the genito-femoral nerves (cyclists)

2. Obturator nerve entrapment (skaters)

3. Sciatic nerve compression

a. piriform muscle syndrome

b. hamstring muscle syndrome

4. Lower lumbar sacral nerves referred pain

Other 1. Sacroilitis

2. Avulsion of the varius muscle attachments (internal and external oblique, latissimus dorsi, paraspinalmuscles, fascia from gluteus medius muscle)

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thickness in different subjects. It often contains a cavity inits interior aspect, probably formed by the softening andabsorption of the fibrocartilage, as it rarely appears beforean individual’s tenth year of life and is not lined bysynovial membrane [3, 4]. This cavity is larger in thefemale than in the male.

The symphysis pubis is richly innervated with branchesfrom the pudendal and genitofemoral nerves, and its bloodsupply is derived from branches of all major vessels in thearea, including the obturator, internal pudendal, inferiorepigastric, and medial femoral circumflex arteries [4, 5].

The innominate bones function as arches, transferringthe weight of the upright trunk from the sacrum to the hips.The symphysis connects these two weight-bearing arches,and circumferential ligaments maintain the mechanicalintegrity. The ligaments of this articulation are: the anteriorpubic ligament, the posterior pubic ligament, the arcuate(inferior) pubic ligament, and the interpubic fibrocartilag-enous lamina. The superior pubic ligament attaches to thecrest and to the tubercle of the pubic bone, while theanterior pubic ligament consists of several superimposedlayers, which pass across the front of the articulation. Thesuperficial fibres pass obliquely from one bone to the other,decussating and forming an interlacement with the fibres ofthe aponeuroses of the external oblique and the medialtendons of origin of the recti abdominis. The deep fibrespass transversely across the symphysis and are blendedwith the fibrocartilagenous lamina. The thin posterior pubicligament merges into the intrapelvic abdominal wall fascia.These three ligaments contribute little on their own to theoverall stability of the joint. The thick inferior pubicligament (arcuate ligament), which forms an arch of toughfibres that stretch from both inferior rami and blend

superiorly with the interpubic fibrocartilagenous lamina,provides most of the joint’s stability (Fig. 1) [3, 4].

The main muscles that play an important role instabilising the symphysis pubis are the abdominal muscles(rectus abdominis, external, and internal oblique) and theadductor muscles. The recti are paired strip-like musclesthat are separated at the midline by the linea alba. Eachmuscle has two tendinous origins: the lateral is attached tothe crest of the pubis, the medial interlaces with its fellowof the opposite side and is connected with the ligamentscovering the front of the symphysis pubis, and, together,they form a muscle mass that inserts onto the fifth toseventh costal cartilages. Studies have shown that there iscontinuation of the rectus abdominis tendon and aponeuro-sis over the anterior symphysis pubis and it is applied to thecapsular tissues and fibrocartilage disk. The aponeuroses ofthe internal and external oblique and transverses abdominisfuse to form the linea alba, a strong midline fibrousstructure that is firmly attached to the xyphoid processabove and the pubic symphysis below.

The ligament that joins the iliac spine to the pubictubercle is the inguinal ligament (IL), which is essentiallythe folded-up lower border of the external oblique muscle,the outermost of the three muscles of the anteriorabdominal wall. The lower aponeurotic part of the externaloblique muscle forms the anterior wall of the inguinalcanal. Immediately superior and lateral to the pubic tuberclea V-shaped gap in the external oblique aponeurosis formsthe external inguinal ring. The folded lower order of theexternal oblique aponeurosis forms a gutter that constitutesthe floor of the inguinal canal (Fig. 2).

The inner two muscles, the internal oblique and thetransverses abdominis, both of which arise, in part, from the

Fig. 1 Diagram of the anteriorpelvis, demonstrating the ingui-nal ligament passing betweenthe anterior superior iliac spineand the pubic tubercle and theadductor longus origin showingits close relationship to thesymphysis pubis. The superiorand inferior arcuate ligamentsare also shown

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lateral part of the IL, join in the medial aspect to formthe conjoint tendon, which has a free edge that arches overthe spermatic cord or round ligament to attach itself to thepectineal line. The conjoint tendon, therefore, forms theroof and posterior wall of the inguinal canal (Fig. 3).

Deep in relation to the arch of the conjoint tendon is theweak transversalis fascia, through which the round ligamentor spermatic cord exits the abdomen to form the internalring (Fig. 3), (4).

The inguinal ligament extends medially to the anteriorpubic symphysis capsular tissues; the adductor longus alsoattaches to these capsular tissues, whereas the adductor brevishas capsular attachments in fewer than half of cases. Incontrast, gracilis and adductor magnus muscles, althoughattached to the pubic bone, have no symphyseal attachments.The rectus abdominis, inguinal ligament, adductor longus andbrevis muscles are, therefore, intimately related to thesymphysis pubis capsular structures and disk [6], (Fig. 4a–d).

Because of their attachment to the thoracic cage proximallyand the pubis distally, the abdominal muscles act synergisti-cally with the posterior paravertebral muscles to stabilise thesymphysis, allowing single-leg stance while balance is main-tained and contributing to the power and precision of thekicking leg. The adductor muscles all insert on the poster-

omedial aspect of the femur (linea aspera). The adductors,because they stabilise the symphysis by bringing the lowerextremity closer to the pelvis, are antagonists to the abdominalmuscles. In addition, the adductor muscle group transmitsmechanical traction forces towards the symphysis pubis duringits activity as a prime mover in soccer push pass, tackling andthe directing of the soccer ball (Fig. 4a, c, d). Imbalancesbetween the abdominal and adductor muscle groups disruptthe equilibrium of forces around the symphysis pubis.

Radiographic technique

Plain radiography is often the first line of investigation inchronic groin pain, primarily to assess the symphysis forosteitis pubis and the hip joint for degenerative joint diseaseand to exclude stress fracture. A standard antero-posterior(AP) view of the pelvis is suggested.

Magnetic resonance imaging technique

It is important that a surface coil (dedicated pelvis phasedarray) be used, placed in the midline and centred over the

Fig. 2 Diagram illustrating thesuperficial (external) inguinalring formed by a V-shaped gap inthe external oblique aponeurosis

Fig. 3 Diagram illustrating thedeep inguinal ring in the trans-versalis fascia and the conjointtendon, which forms the roof ofthe inguinal canal laterally andposterior wall medially deepnear the superficial inguinal ring

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symphysis pubis. The imaging planes should includecoronal oblique and axial oblique sequences, planned froma midline sagittal scout image (angulation 15° to theperpendicular and orientated to the long axis of thesymphysis). We prefer to use an intermediate weightedfast-spin-echo sequence [time to repeat (TR) 3,500 ms, timeto echo (TE) 35 ms] with a 512 pixel/256 pixel, 3 mm slicethickness, with no interslice gap, and a 20 cm field of view.Either proton density fat-suppressed or short-tau inversionrecovery (STIR) sequences are also performed in theseplanes to identify oedema in both bone and soft tissue.Furthermore, we routinely perform axial and coronal protondensity (TR 3,000 ms, TE 30 ms] scans through the lowerpelvis to assess the recti and inguinal ligament complexes(Fig. 5).

Ultrasound technique

The patient is examined while lying in a supine position. Ahigh-resolution linear array transducer of 10 MHz or greaterfrequency is recommended. We start by identifying thepubic tubercle, then orientate the probe along the direction

of the inguinal ligament, following it to the anterior inferioriliac spine. It is also examined in the transverse plane(Fig. 6a). The inferior epigastric vessels should beidentified so that a landmark is obtained for the deepinguinal ring, which lies lateral to these vessels (Fig. 3).The inguinal canal should be examined with the patient in arelaxed state and with abdominal straining. The contra-

Fig. 4 Axial and coronal protondensity (PD) magnetic reso-nance images demonstrate mus-cle anatomy: (a) gracilis muscleorigin anteriorly (white arrow),adductor longus (short whitearrow), brevis (white arrow-head) and magnus (white doublearrowhead). b Axial section at ahigher level shows the pectineusmuscle (white arrow). c Adduc-tor magnus arising from theinferior pubic ramus (white ar-row). d Coronal section showinggracilis (long white arrow) andadductor longus (short whitearrow) and brevis (whitearrowhead)

Fig. 5 Coronal proton density (PD) magnetic resonance imagedemonstrating a normal inguinal ligament (white arrows) extendingfrom the anterior superior iliac spine to the pubic tubercle medially

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lateral side is examined, even if asymptomatic, forcomparison. The pubic symphysis is assessed firstly byidentification of the anterior pubic ligament (Fig. 6b), therectus abdominis tendon and aponeurosis blending withthe capsular tissue, and then more inferiorly so that theadductor longus origins may be seen. Finally, the femoralcanal should be assessed for the presence of a femoralhernia; again, it is important that the patient be asked tostrain.

Pelvic stress fractures

Stress fractures can occur in normal or abnormal bone thatis subject to repeated cyclic loading, with the load beingless than that required to cause an acute fracture. Two typesof stress fractures are recognised: a fatigue fracture, whichresults from the application of abnormal stress or torque ona bone with normal elastic resistance, and an insufficiencyfracture, which occurs when normal stress is placed upon abone with deficient elastic resistance [7–11]. In general, theterm stress fracture is used to describe fatigue fracturesrather than insufficiency fractures. The muscles and soft

tissues of the pelvis protect the skeleton from the effects ofrepeated stress, explaining the greater incidence in femaleathletes [12, 13].

Stress fractures are common in endurance athletes andmilitary recruits. Insufficiency fractures can occur inathletes with osteoporotic or osteomalatic bone, typicallyseen in young female athletes with nutritional or hormonalinsufficiency, or both. Pelvic stress fractures in athletesmost commonly involve the inferior rubic ramus andfemoral neck but can also involve the superior pubicramus, acetabulum and sacrum [14–16]. Stress fracture ofthe femoral neck, in particular, can have potentially seriousconsequences if not diagnosed promptly, as it can lead tocomplete fracture and potential resultant avascular necrosis[17].

Insufficiency fractures have a predilection for thesuperior and inferior pubic rami and the iliac blades. Theyusually present with chronic pelvic pain in women. Non-union of insufficiency fractures may result in a bony massthat can mimic a tumour. Patients usually present withexercise-induced groin and thigh pain to the point ofinability to run and will often have pain with axial loadingor with standing or hopping on the involved leg. Physicalexamination may also reveal focal tenderness at the site ofstress fracture.

Plain radiographs are often normal, especially early on, andfollow-up films may only demonstrate abnormalities in 50%of cases [20]. Bone scintigraphy has a high sensitivity butlacks specificity and spatial resolution. Magnetic resonance(MR) imaging has replaced bone scintigraphy as themodality of choice, due to its superior specificity [21]. Inthe early phase (within 3 weeks of the onset of symptoms),bone marrow oedema and haemorrhage may be identified onfluid-sensitive sequences. After 3 weeks, following resolu-tion of oedema, a pattern of hypointense signal secondary tosclerosis at the site of fracture may be observed; this might,however, be obscured by fat on both inversion recovery andfrequency selective fat-suppression sequences. Evaluation ofsuspected stress fracture can be made with a T1-weightedspin-echo sequence in which the hypointense line iscontrasted against normal hyperintense marrow fat. Themagnetic resonance imaging (MRI) classification of stressfractures is shown in Table 2 [22]. Figure 7 shows typical

Fig. 6 Ultrasound of the groin (a) demonstrating normal appearanceof the inguinal ligament, seen as an echogenic linear structure inlongitudinal section (white arrows). b Transverse ultrasound demon-strating the anterior pubic ligament (arrows) seen as a relativelyhypoechoic structure

Table 2 MRI classification of stress fractures [22]

MRI classification of stress fractures [22]

Grade 1: endosteal marrow oedema

Grade 2: periosteal and endosteal marrow oedema

Grade 3: muscle, periosteal and endosteal marrow oedema

Grade 4: fracture line

Grade 5: callus in cortical bone

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appearances of grade 3 stress injury. Grades 1 and 2 MRIchanges may be present in asymptomatic athletes [23].

On follow-up, MRI usually demonstrates a bone marrowsignal intensity that has returned to normal on fluid-sensitivesequences at 3 months; bone scintigraphy is less useful, asabnormal uptake persists for up to 8–10 months, althoughintensity usually decreases within 3–6 months [24, 25].

Osteitis pubis

Osteitis pubis, also known as pubalgia, is a painful inflam-matory condition of the symphysis pubis and surroundingmuscle fascia that was first described by Beer in 1924 andlater by Spinelli in 1932 as a rectus abdominis adductorissyndrome. It is postulated that osteitis pubis is caused byrepeated traumatic or exertional stresses on the fascia andthe joint, resulting in traction microtrauma [18, 19]. Muscleimbalances between the abdominal and hip adductormuscles have been suggested as an aetiological factor.The imbalance disrupts the equilibrium of forces aroundthe symphysis pubis, predisposing the athlete to asubacute periostitis caused by chronic microtrauma. Thismicrotrauma exceeds the rate at which the tissues canrepair, resulting in tissue degeneration. The symphysispubis acts as the anterior axis for innominate rotationduring normal walking and is also subject to superiorshear forces during single-leg stance. Jumping, twisting,or turning motions during sprinting, cutting and kickingactivities have been implicated in the pathogenesis ofosteitis pubis [26]. These activities are most prevalent insports such as soccer, Australian rules football andhockey, with a reported incidence in soccer players of14–28% [1].

The clinical picture includes pain when kicking oradvancing the leg forward during the swing phase of gait,focal pain or tenderness at the pubic symphysis, and pain inthe lower portion of the abdominal muscle groups.

Radiographic assessment of the pubic symphysis inyoung men may be problematic, as ossification in thisregion is variable and normal findings can be misinter-preted. Imaging findings include non-specific irregularity ofthe cortical margin, pubic symphysis widening (more than7 mm), subchondral cystic changes, subchondral resorption,fragmentation, joint irregularity and, in chronic cases,sclerosis, and osteophytic bridging [27]. Bone scintigraphydemonstrates increased uptake about the symphysis pubis,but a negative scan does not exclude the diagnosis [28].

MR is the imaging method of choice to demonstrateparasymphyseal marrow oedema with symphyseal fluid andperipubic soft tissue oedema on fluid-sensitive sequences(Fig. 8). In addition, it is common to observe oedema in theadjacent muscle belly of the adductor brevis in acute cases(Fig. 9). Although oedema can be seen in asymptomaticathletes, more marked changes appear to correlate withsymptoms [27, 28].

Fig. 7 Coronal MR of the pel-vis. a Proton density turbo-spin-echo image reveals abnormallow signal intensity (whitearrow) within the superior pubicramus, with surrounding lowsignal intensity of marrowchange. b Proton density fat-saturated (FS) images revealchanges in high signal intensitywithin the marrow adjacent tothe stress fracture (white arrow)and periosteal high signal inten-sity (white arrowhead) repre-senting oedema

Fig. 8 Osteitis pubis. Axial PD fat-saturated (FS) MR imagedemonstrates bilateral parasymphyseal marrow oedema (black arrow-heads) and oedema bilaterally within the adductor brevis origins(white arrows)

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Chronic changes involving the pubic symphysis includeirregularity, medial subchondral oedema and cysts. Widen-ing of the symphyseal cleft may be observed in chroniccases (Fig. 10). These chronic changes have been shownnot to correlate with the current symptomatic side inathletes and are also seen in asymptomatic athletes [27].Table 3 summarises acute and chronic MRI findings.

Management of osteitis pubis is difficult, there being acontinuous debate between conservative policy and surgicalintervention. Conservative treatment usually involves rest,oral medication with non-steroidal anti-inflammatory drugs,daily use of therapeutic modalities (cryomassage, ultra-sound, or electric stimulation), a progressive rehabilitation

programme with an emphasis on the strengthening of thesurrounding muscles, and the use of non-steroidal anti-inflammatory drugs. However, complete recovery can takeover 6 months. Earlier return to full activity has beenreported following image-guided injection of corticosteroidand local anaesthetic directly into the joint [29, 30].

Surgical management includes curettage, and, in thesetting of instability, arthrodesis may be performed [31].Wedge resection of the pubic symphysis can be performedas a last resort in cases that are refractory to non-operativetreatment; however, this can be complicated by pelvicinstability [32]. Recently, elite athletes have been treatedintravenously with bisphosphonates [33].

Symphyseal disc degeneration

With an individual’s advancing age, the fibrocartilage of thesymphysis pubis, which serves to absorb impact and todissipate shear forces, develops a small central fluid cavity orcleft. This cleft is identified clearly as a central focus of highsignal intensity on T2-weighted/proton density fat-suppressedand STIR images. A ‘secondary cleft’ may also be seen,continuous with the physiological cleft within the symphysealfibrocartilage, and is manifested as an extension of fluid signaloutside the pubic symphysis to one or both sides (Fig. 11).The side of fluid extension within the secondary cleft hasbeen shown to correlate with symptoms [34]. It is thought torepresent a capsular injury to the pubic symphysis secondaryto adductor avulsion, be it partial or complete. It is likely thatrepetitive traction of the adductor enthesis leads to micro-trauma and tearing. This is exacerbated by extrusion of thefibrocartilagenous disc, undermining the arcuate ligamentcomplex and extruding into the torn adductor origin(Fig. 12). Similar to intervertebral discs herniation, symphy-seal disc extrusion is seen with symphyseal disc degenera-tion. The symphyseal disc is seen most frequently to extrude

Fig. 9 Osteitis pubis. Coronal PD fat-saturated (FS) MR imagereveals severe bilateral parasymphyseal marrow oedema with bilateralmarked adductor brevis origin oedema and bilateral subchondral cysts(white arrows)

Fig. 10 Chronic osteitis pubis.a Axial computed tomography(CT) scan of the pubic symphy-sis demonstrates bilateral jointline irregularity, subchondralcyst formation and minor sub-chondral sclerosis (blackarrows). (b) Axial CT scan in adifferent patient demonstratesmarked osteolysis with associat-ed soft tissue thickening of theanterior symphyseal joint (whitearrowheads)

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inferiorly or posteriorly in relation to the pubic symphysis.This degeneration of the symphyseal disc is common in eliteathletes and may be asymptomatic.

Adductor longus dysfunction

Chronic groin pain secondary to adductor muscle dysfunc-tion can originate from two different conditions, namelychronic myotendinous strain or tenoperiosteal disease(enthesopathy). Management of the two conditions isdifferent, with aggressive rehabilitation advocated forchronic musculotendinous strain. Tenoperiosteal disease isthought to result from repetitive microtrauma, leading tomicro-tears that result in a long-term cycle of tendon injuryand repair. This can then lead to muscle spasm, atrophy andweakness. The adductor longus tendon is most commonlyaffected; the gracilis is rarely involved. The other adductormuscles (brevis and magnus) arise more posterolaterallyand are rarely involved. Osteitis pubis and adductorenthesopathy are mechanically related, and they frequently

coexist as an injury; subsequent weakening and alterationof the biomechanics of the adductor muscles can lead toinstability at the pubic symphysis.

Groin or medial thigh pain is the most commonsymptom, exacerbated by exercise or kicking. Clinically,patients with adductor dysfunction have tenderness local-ised to the adductor longus origin, pain on passivestretching of the adductors, and pain on adduction of thethigh against resistance.

MRI findings in active enthesopathy demonstrate peri-ostitis and adjacent marrow oedema, with oedema in theadjacent muscles and thickening of the adductor tendinousinsertion. Gadolinium enhancement of the adductor enthe-sis has been demonstrated to correlate with the symptom-atic side [28].

Ultrasound of the adductor insertion shows tendonthickening and interstitial tearing, and neovascularity maybe demonstrated on colour Doppler (Fig. 13).

Conservative treatment includes rest, icepacks, non-steroidal anti-inflammatory medications, and physiotherapy.Athletes with adductor-related groin pain but normal MRI

Description

Acute MRI findings

∙ Juxta-articular pubic bone marrow oedema

∙ Oedema within adductor brevis muscle

∙ Irregularity of the pubic symphysis

∙ Enhancement of marrow oedema on post-contrast T1-weighted images

Chronic MRI findings (disease present >6 months)

∙ Degenerative changes

Subchondral cysts/subchondral sclerosis

Osteophytosis

∙ Incongruity of the joint in the anterosuperior plane or superior inferior plane

Table 3 Osteitis pubis, acuteand chronic MRI findings

Fig. 11 Coronal PD fat-saturated(FS) MR images from twopatients (a and b) demonstratebilateral parasymphyseal marrowoedema, beaking of the superiorpubic symphysis (hypertrophyof the superior pubic ligamentand osteophyte formation,black arrows). There is asecondary cleft interposedbetween the inferior surface ofthe pubic bone and the adductorlongus origin on the right ina (white arrow) and on the leftin b (white arrow)

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findings have been shown to respond well to a singleentheseal pubic cleft injection with local anaesthesia andsteroid; however, athletes with evidence of enthesopathy onMRI only obtain short-term relief from injection [35].

Acute muscle tear/avulsion

In acute injuries of the adductor group of muscles the adductorlongus muscle is most commonly involved. The site of injurywithin the functional muscle unit depends on the maturity ofthe athlete. In young, skeletally mature, athletes the mainareas of weakness are the myotendinous junction and themuscular aponeurosis [36, 37]. A similar injury in askeletally immature patient will result in apophyseal avul-sion. In the more mature athlete the degenerated tendon cantear. The adductor muscles are particularly vulnerable insoccer players. It is thought that proximal adductor longustears are more common in experienced athletes, possibly dueto the relative weakness produced by an underlyingtendinopathy. Pre-existing symphyseal disc degeneration isalso thought to predispose the athlete to tendon avulsion, asextrusion of the disc undermines the adductor longus origin(Fig. 14). Avulsion of the common adductor origin insertion,gracilis and rectus abdominis aponeurosis may result ininstability and anterior subluxation of the pubic symphysis.

There is a well-established clinical grading system formuscle tears that has three components, from grade 1 (lessthan a 5% loss of function), grade 2 (severe, with somepreserved function0 to grade 3 (complete muscle tear andfunctional loss [38]).

On ultrasound and MRI, grade 1 muscle tears can shownormal appearances or a small area of focal disruption (lessthan 5% of the muscle volume), with haematoma and peri-fascial fluid relatively common. A grade 2 injury corre-sponds to a partial tear, with muscle fibre disruption seen(over 5%) but not affecting the whole muscle belly. Grade 3injuries are complete muscle tears with frayed margins andbunching of the muscle on dynamic ultrasound assessment.Compared with MRI, ultrasound allows the demonstrationof muscular architecture at a higher resolution, and dynamicmuscle assessment, and it is less time consuming. However,in athletes with large muscle bulk, depth of resolution canlimit visualisation, and in these instances, MRI is moreuseful. Once the adductor tear has occurred (or if thetendinous origin is completely avulsed), then chronicsymptoms may disappear due to defunctioning of thecausative overload process, the tear acting as a functionalrelease. During healing, ultrasound can demonstrate therestoration of normal muscle architecture and can be usedto determine rehabilitation intensity. MRI is less useful inassessing the stage of healing, as abnormality of signalintensity persists throughout the different stages [39].

Ilio-psoas injury

Ilio-psoas tendinosis is an uncommon cause of sports-related groin pain. It is most commonly seen in kicking-

Fig. 13 Adductor longus enthesopathy. a Longitudinal ultrasound ofthe right adductor longus shows marked swelling and hypoechoicchange (white arrows) of the tendon at its insertion into the pubicsymphysis (PS); the adductor longus (AL) muscle appears normal. bPartial tear of the origin at the under-surface (white crosses)

Fig. 12 Coronal PD fat-saturated (FS) MR image of the pelvisdemonstrating a high signal intensity cleft extending infero-laterallyon the right (white arrowhead) with oedema in the adductor longus(long white arrow). There is also extensive oedema in the left adductorbrevis (short white arrow) due to tears at the musculo-tendinousinsertion. There is no pubic symphyseal oedema to indicate osteitispubis

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related sporting activities and is associated with repetitivehip flexion. It is also seen in patients following total hipreplacement and is caused by impingement of a mal-positioned acetabular cup on the ilio-psoas tendon on hipflexion. Patients present with groin pain exacerbated by hipflexion and adduction. MRI demonstrates thickening orattenuation of the tendon along its course or at its insertion.High signal intensity is seen around the tendon on MRfluid-sensitive sequences. There may be an associated ilio-psoas bursitis. Ultrasound can be useful for image-guidedinjection of local anaesthetic and steroid into the peri-tendinous tissues if rehabilitation has proved unsuccessful.

Ilio-psoas spasm

This condition most commonly affects athletes, sprinters andcricketers, and is thought to occur secondary to over-training.Psoas spasm is also often seen secondary to either osteitispubis or hip joint dysfunction. Athletes present with hip andgroin symptoms. There are no specific imaging findings, but itis useful to exclude other causes of groin pain. The spasmmayrespond to an ultrasound-guided injection of a long-actinglocal anaesthetic (e.g. bupivacaine) into the tendon sheathstripping it away from the muscle.

Obturator nerve entrapment

The obturator nerve is formed by the anterior rami of theL2, L3 and L4 lumbar nerve roots as part of the lumbarplexus in the psoas muscle (Fig. 15). It emerges from themedial border of the psoas at the pelvic brim, traversing thesacro-iliac joint behind the common iliac vessels before

running forward on the lateral pelvic wall in the anglebetween the internal and external iliac vessels, to passthrough the a fibro-oseous tunnel (Fig. 16). The obturatorsulcus of the pubic bone forms the roof of this tunnel; thefloor consists of the internal and external obturator musclesand their covering fascia [40]. Here, the nerve separatesinto anterior and posterior divisions: the anterior divisioncontributes articular branches to the hip joint, and theposterior division terminates by supplying branches tothe knee joint. The motor distribution of the nerve is tothe adductor muscles, gracilis and obturator externus;

Fig. 14 Adductor longus avul-sion. a Coronal PD fat-saturated(FS) image demonstrating avul-sion and retraction of the ad-ductor longus tendon (whitearrow), with blood fluid prod-ucts interposed between the pu-bic symphysis and tendon (blackarrow); note the pre-existingsymphyseal disc degeneration(white arrowhead). b CoronalPD image demonstrating avul-sion and retraction of the ad-ductor longus tendon (whitearrow), with large amounts ofblood fluid products (blackarrows)

Fig. 15 Diagram illustrating the obturator nerve formed by theanterior rami of L2–L4. After exiting the obturator canal it separatesinto anterior and posterior divisions

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sensation to the medial thigh is conveyed by sensory fibresin the anterior division.

The mechanism of entrapment resulting in obturatorneuropathy is unclear [41]. The clinical, electrophysiolog-ical and surgical findings suggest that the entrapmentoccurs at the level of the obturator foramen and proximalthigh and is likely to represent fascial entrapment of thenerve at this level. Imaging findings are few; however, inthe acute setting, high signal intensity consistent withdenervation injury can be seen in obturator-suppliedmuscle. There is a characteristic clinical pattern ofexercise-induced medial thigh pain commencing in theregion of the adductor muscle origin and radiating distallyalong the medial thigh. Needle electromyography demon-strates denervation of the adductor muscles. This conditionis most commonly seen in wheelchair athletes. Surgicalneurolysis provides the definitive cure, with athletes beingable to return to competition within weeks [41]. CT-guidedobturator nerve block using the posterior approach may alsoprovide relief of symptoms [42] (Fig. 17).

Anterior abdominal wall muscle injuries

In players of racquet sports and hockey the abdominalmusculature plays a significant role in trunk and corestability, providing a mechanical link between the lowerand upper extremities. Trunk rotation plays a significantrole in generating the force required to hit the ball or puck.Injury to the anterior abdominal wall results in pain,tenderness, and withdrawal from training and competition

[43]. It is thought that after a strain injury the muscle isweakened and has an increased risk of further injury. It hasbeen demonstrated that in elite tennis players there ishypertrophy of the contralateral rectus abdominis muscle(non-dominant arm side) thought to be a consequence ofincreased strain transferred through the muscle [44](Fig. 18). Sonography has been shown to be a sensitivetechnique in detecting tears within the rectus abdominismuscle which occur within its deep fibres below theumbilicus.

On MRI, acute injuries are seen as areas of fibrildisruption. Injuries are easier to identify if haemorrhageand muscle oedema are present. This is manifested as highsignal intensity seen on the deep surface of the muscle [44](Figs. 18 and 19).

Sports hernia

In the literature the term sports hernia is a general term thatis used describe two different inguinal pathologies: poste-rior inguinal wall deficiency and Gilmore’s groin [45].Posterior inguinal wall deficiency is a result of weakeningand possible tearing of the conjoint tendon and transversalisfascia which forms the posterior wall of the inguinal canal[46], whereas Gilmore’s groin involves tears in the medialaspect of the external oblique aponeurosis which forms theanterior wall of the canal and forms the external (superfi-cial) ring [47]. In both theses conditions no hernia isdetectable. Sports hernias should be thought of as inser-tional fascial deficiencies of the conjoint tendon andexternal oblique aponeurosis. A patient may have tears

Fig. 16 Axial T1-weighted MR image at the level of the mid femoralhead demonstrates the obturator nerve and vessels within the obturatorcanal (white arrow)

Fig. 17 Axial CT scan of the pelvis demonstrating needle position onthe lateral pelvic wall to target the obturator nerve (white arrow)

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involving the conjoint tendon, transversalis fascia andexternal oblique (Fig. 20). The cause of the patient’s painand rapid response to various surgical interventions may bea result of sensitisation of nerves, in particular the genitalbranch of the genito-femoral nerve, which may be inflamedor encased in scar tissue. Athletic pubalgia may be a moreappropriate term for these entities, as a true hernia is notpresent [48]. Sports hernia is most commonly seen inathletes who participate in sports that require repetitivetwisting and turning at speed, such as hockey, soccer andtennis. Sports hernias are thought to arise through overuse.Hip adduction, abduction, and flexion/extension produce a

shearing force across the pubic symphysis, leading to stresson the inguinal wall musculature perpendicular to the fibresof the fascia and muscle.

Injury to the conjoint tendon, which forms the posteriorwall of the inguinal canal, results in loss of integrity of thecanal and probably represents an early spectrum of injuryfor which direct hernia formation is the end result. Thedeficiency is found in 80–85% of those who haveundergone herniorrhaphy for chronic groin pain [49](Fig. 21). Gullmo suggested that pain in these circum-stances may be caused by distension of the peritoneum orstretching of the ilio-inguinal nerve [51]. Gilmore popu-larised the syndrome of groin disruption as ‘Gilmore’sgroin’ in the early 1990s [51]. This condition involves themedial aspect of the external oblique muscle, which formsthe anterior wall of the inguinal canal as well as thesuperficial (external) inguinal ring, which is dilated.

Sports hernias usually present with an insidious onset ofunilateral groin pain as the most commonly reportedsymptom. Many patients, however, describe a sudden

Fig. 19 Coronal PD MR image showing a tear of the left lower rectusmuscle (white arrow)

Fig. 18 Axial PD MR image shows hypertrophy of the left rectusmuscle in a professional tennis player. There is an area of high signalintensity due to muscle tear on the deep epimysial surface, withhaemorrhage (white arrow)

Fig. 20 Longitudinal ultrasound (US) image of the inguinal ligamentdemonstrating (a) hypoechoic disruptions of the external obliqueaponeurosis (white arrows). b In the same patient bulging of theposterior inguinal wall (white arrows) is demonstrated, with obliter-ation of the inguinal canal on straining (black arrowhead). c In adifferent patient, hypoechoic abnormality (white arrows) of theinguinal ligament is seen (black arrowhead highlights the normalligament)

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tearing sensation. The pain usually occurs during exercise,although it can occur at lower activity levels. Physicalexamination may reveal local tenderness over the conjointtendon, pubic tubercle and mid-inguinal region, or a tenderdilated superficial ring. Surgical intervention is consideredfollowing a trial of conservative treatment. Although it maybe useful to attempt conservative measures for 6–8 weeks,it should be noted that non-operative therapy is seldomsuccessful. There is, however, no consensus to support anyparticular surgical procedure.

Gilmore described the surgical restoration of the tornexternal oblique aponeurosis and conjoint tendon by

modified herniorrhaphy, with plication of the transversalisfascia and polyglactin repair of the conjoint tendon. Thelatter is then approximated to the inguinal ligament with anylon darn. The external oblique is repaired, and the woundis closed in layers. An adductor tenotomy is also performedif there are adductor symptoms [45].

A number of different modified repairs of the posteriorwall deficiency have also been described. Malycha andLovell repair the posterior inguinal wall in two layers; acontinuous suture is inserted from the pubic tubercle to theinternal ring, followed by a second layer (with a loose darnover the layer) [52]. Laparoscopic repair is also described;

Fig. 21 Laparoscopic view of the left posterior inguinal walldemonstrating (a) multiple tears in the fascia transversalis (annotatedwhite arrows) just lateral to the pubic tubercle (PT). b Multiple

disruptions in the fascia transversalis (annotated white arrows). . ILinguinal ligament, FC femoral canal. Image courtesy of Mr DavidLloyd, Leicester

Fig. 22 Summary algorithm forthe investigation and treatmentof groin pain in the athlete

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synthetic and biological mesh has been advocated toreinforce the posterior wall of the inguinal canal andchange pressure onto mesh rather than inguinal ligament.Some surgeons divide the inguinal ligament and any scartissue at the same time.

Postoperatively, most athletes return to sports within 6–12 weeks after specific rehabilitation targeted at abdom-inal strengthening, adductor muscle flexibility, and agraduated return to activity. The reported symptomaticcure rates for herniorrhaphy in sports hernia is 63% to94%, compared to 99% for many studies of conventionalhernia repair [49]. It has been suggested that the poorersuccess rate may reflect failure to attend to any associatedadductor problem.

MRI and ultrasound can be used to exclude co-existingabnormalities prior to the patient’s undergoing a groinrepair. Posterior inguinal wall deficiency can be demon-strated sonographically, as contraction of the anteriorabdominal wall results in loss of the normal valve-likeeffect of the canal. Hence, the posterior inguinal wall isdisplaced anteriorly, as opposed to becoming taut(Fig. 20b). Furthermore, there is a loss of the mildphysiological compression of the spermatic cord, whichis normally evident by a decrease in the size of thepampiniform plexus, which, paradoxically, increases insize. Until recently, Gilmore’s groin remained a clinicaldiagnosis and a radiological diagnosis of exclusion.However, high-resolution MRI and ultrasound may iden-tify subtle tears and defects within one or more of thestructures that inserts around the groin region. Thesedeficiencies in the inguinal ligament are best demonstratedon ultrasound (US) with training, but this remains highlyoperator dependent.

Conclusion

Groin pain is a complex spectrum of abnormalities that canoften overlap. Figure 22 outlines an algorithm that is usedat our institution to investigate an athlete presenting withgroin pain.

In conclusion, knowledge of the pertinent anatomy isrequired for the interpretation of sports-related groininjuries. Careful MR imaging is recommended, as this willimprove diagnostic capabilities. MR imaging is favouredover ultrasound as the initial imaging modality as it morereadily allows symphyseal abnormalities to be identified. Ifthe initial MRI fails to demonstrate an abnormality,ultrasound is useful for adductor enthesopathy and in theidentification of rare occult hernias not identified on theinitial study. We have illustrated the imaging findings forthe more common conditions encountered in sports-relatedgroin pain.

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