U L T R A S O U N DC L I N I C S

Ultrasound Clin 2 (2007) 595–615

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Common Tendon and MuscleInjuries: Lower ExtremityTheodore T. Miller, MD, FACRa,b,*

- Sonographic appearance of injury- Hip and thigh

Abductor musclesSnapping hip syndromeIliopsoas tendonAdductor musclesTensor fascia lataRectus femoris muscleHamstrings

- Knee and calfDistal quadriceps tendon rupturePatellar tendinosis and tear

Jumper’s knee (patellar tendinitis)Osgood-Schlatter disease and

Sinding-Larsen–Johansson diseaseThe posterolateral cornerCalf

- AnkleAchilles tendonFlexor tendonsPeroneal tendons

- Summary- References

The lower extremity is the most commonly for further evaluation of soft tissue injury. Although

injured body part in many sports, affecting athletesat all levels of competition ranging from gradeschool to professional and elite amateur sports[1–4]. Although many injuries are sport-specific[5–10], common trends of muscle and tendoninjury affect both male and female athletes[4,11,12]. One large survey of high-school athletesin the United States in 2005 found that football wasthe most common cause of lower extremity injuriesin boys, whereas soccer was the most common ingirls; muscle strains and contusions were the secondand third most common injuries after ligament in-jury, with the ankle, knee, and thigh the three mostcommon sites of injury in descending order [3].

The imaging evaluation of the painful or injuredlower extremity should always begin with radio-graphs, but advanced imaging is often necessary

a Department of Radiology and Imaging, Hospital forNY 10021, USAb Weill Medical College of Cornell University, 1300 York* Department of Radiology and Imaging, Hospital foNY 10021.E-mail address: millertt@hss.edu

1556-858X/07/$ – see front matter ª 2007 Elsevier Inc. All rightsultrasound.theclinics.com

MR imaging is the gold standard, providing ananatomic overview and excellent demonstrationof the bony structures, articular surfaces, and thesurrounding soft tissues, sonography is quickly per-formed, has greater resolution than MR imaging[13], allows dynamic evaluation of tendons andmuscles, and can guide percutaneous procedures.Moreover, the advent of sonographic extended fieldof view imaging allows the demonstration of theentire length or cross-section of an area of interest,matching the ability of MR imaging to displaya large anatomic region.

Sonographic appearance of injury

Muscles usually tear at the muscle fiber–centraltendon attachment (the musculotendinous

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junction), or less often at the myofascial junction ofthe epimysium along the superficial surface of themuscle. Sonographically, a muscle tear appears asdisruption of the normal pennate architecture,either with focal hyperechogenicity from interstitialhemorrhage or hypoechogenicity caused by frankhematoma formation. The outer fascial layer sur-rounding a muscle may occasionally tear, allowingthe muscle to herniate through the fascial rent dur-ing muscle contraction; dynamic scanning duringmuscle contraction can demonstrate the muscleherniation, whereas static imaging with the muscleat rest may fail to show the abnormality.

Tendon injury has a spectrum of appearances,depending on the severity and chronicity of theabnormality. Microtears caused by repetitive over-use lead to intrasubstance degeneration, whichmay demonstrate (1) areas of mucinous changethat manifest as replacement of the normal echo-genic fibrillar pattern by ill-defined hypoechoicregions; (2) neovascularity caused by angiofibro-blastic proliferation [14], which can be shownwith color or power Doppler imaging; or (3) echo-genic foci of calcification and heterotopic ossifica-tion. Continued microtearing may lead to franktear, which may be purely interstitial or involvethe tendon surface. Mild partial tearing may leadto tendon thickening and hypoechogenicity,whereas severe partial tearing causes thinning andattenuation of the tendon, similar to a frayingrope. Rupture of the tendon manifests as tendinousdiscontinuity, with or without retraction [15].

Caution should be exercised when scanning ten-dons to make sure that the sonographic beam isperpendicular to the tendinous structure in what-ever plane is being imaged; a nonorthogonal soundbeam may make the tendon look artifactuallyhypoechoic, mimicking tendinosis or tear, causedby anisotropy. Anisotropy is the property of highlyordered structures, such as tendons, ligaments,and nerves, to vary in their reflective echogenicity

Fig. 1. Anisotropy. (A) Transverse sonographic image of thbeam shows echogenic circular structures. PL arrow is the(B) Transverse sonographic image with the insonating bechogenicity of the two tendons (arrows).

depending on the angle of insonation of the inter-rogating sound beam (Fig. 1).

Hematoma can have a variable sonographicappearance. Some authors have reported a hypoe-choic appearance acutely, which becomes heteroge-neously hyperechoic as the hematoma organizes[16,17], whereas some have reported the reversetemporal appearance [18–20], and others havereported no correlation between time course andsonographic appearance [21].

Hip and thigh

Abductor muscles

An analogy can been made between the gluteusmedius and minimus tendons, which are abductorsof the hip, and the supraspinatus and infraspinatustendons, which assist in abduction of the shoulder.Thus, the gluteus medius and minimus have beentermed the rotator cuff of the hip [22]. Similar tothe tendons of the rotator cuff, the gluteus mediusand minimus tendons are subject to tendinosis,partial tear, and full thickness tear. The adjacentbursae may be concomitantly inflamed or merelydistended due to abnormality of the adjacent ten-don. The bursa most commonly involved is thesubgluteus maximus bursa, also called the greatertrochanteric bursa, which is larger than the subglu-teus minimus and subgluteal medius bursae, andwhich is located over the posterolateral aspect ofthe trochanter [23].

The greater trochanteric pain syndrome is charac-terized by pain and focal tenderness in the region ofthe greater trochanter, which is exacerbated withweight-bearing and hip abduction and usuallyaffects middle-aged and older women. It can becaused by tendinosis and partial or complete tearsof the gluteus medius or minimus tendons,inflammation of any of the three subgluteal bursae,or more commonly a combination of gluteal ten-don abnormality and gluteal bursitis. Most cases

e peroneal tendons with a perpendicular insonatingperoneus longus and PB arrow is the peroneus brevis.am at an angle other than 90� shows marked hypoe-

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are caused by chronic degeneration and overuse,with only a few by prior local trauma [24–27].The fluid-distended bursae appear as discrete hypo-echoic or anechoic collections. The degeneratedtendon is thickened and may appear hypoechoic,and a partial tear appears as either a focal anechoicregion or a hypoechoic linear zone within thetendon (Fig. 2). A complete tear involves the fullthickness of the tendon and may or may not dem-onstrate retraction of the tendon (Figs. 3 and 4);the respective muscle may be atrophic, with lossof volume and increased echogenicity caused byfatty infiltration [28]. Using the appearances of bur-sitis, elongation of the gluteus medius tendon, andtendon discontinuity, Cvitanic and colleagues [25]achieved 93% sensitivity and 91% accuracy for diag-nosing tears of the abductor tendons, whereas Con-nell and colleagues [24] achieved 90% sensitivityand 95% specificity for tear. Connell and colleagues[24] also reported cortical irregularity of the greatertrochanter in 25 of 53 cases, analogous to that seenon the greater tuberosity of the humerus in rotatorcuff tears, and hyperemia on color or power Dopp-ler in only 9 of 53 hips.

Calcification of the gluteus minimus or mediustendon may also be encountered [24], an appearancethat has also been described radiographically [29].

Snapping hip syndrome

The snapping hip syndrome refers to a suddensnapping sensation during hip motion and can becaused by intraarticular and extraarticular causes[30–32]. Intraarticular causes include loose bodies(either from trauma, degenerative arthritis, or syno-vial osteochondromatosis) and labral tear, whereasextraarticular causes are caused by abnormal mo-tion of tendons. The extraarticular causes can befurther classified as lateral, or external, snapping,caused by abnormal motion of the iliotibial band

Fig. 2. Gluteus minimus tendinosis. (A) Longitudinal exgluteus medius and gluteus minimus muscles inserting ospur (arrow) arises from the trochanter. The gluteus minview of the greater trochanter shows a thickened and hyplinear hypoechoic tears along its deep surface (long whitethe subgluteus minimus bursa (black arrow) (also calledmedius tendon is more normal-appearing (short white ar

or gluteus maximus over the greater trochanter,and as medial, or internal, snapping, caused by ab-normal motion of the iliopsoas tendon over theiliopectineal eminence of the pelvis, the anteriorinferior iliac spine, or even the lesser trochanter[33]. Teenagers and young adults are typicallyaffected and may not have any predisposing occu-pational or athletic activity [31,32], although Jan-zen and colleagues [32] reported that four of eightpatients who had a snapping iliopsoas tendonexperienced a preceding traumatic event of hipabduction and external rotation. Regardless ofa medial or lateral origin, the snapping may ormay not be painful [30].

On static imaging, the offending tendon oftenlooks normal, although tendinosis, peritendinousfluid, and iliopsoas bursitis have occasionally beendescribed [30–32]. The imaging diagnosis is made,however, using dynamic sonography to documentthe snap or sudden jerk of the tendon. To evaluatea suspected snapping iliopsoas tendon, the trans-ducer is placed transversely over either the femoralhead or pectineal eminence of the pelvis, and thepatient, lying prone, is asked to flex, externally ro-tate, and abduct the femur (producing a frog lateralposition) and then move back to neutral position. Anormal iliopsoas tendon will have smooth move-ment, but a snapping one will show a sudden jerk,often with a palpable or audible snap. The snapmay occur from medial to lateral or vice versa; ante-rior to posterior; or a rotational movement on itself,and may occur during hip flexion to extension orvice versa [30]. The creation of a flash artifact fromthe fast-moving snap has also been described asa secondary sign of the snapping tendon [34].Even when snapping cannot be shown sonographi-cally, these patients may obtain pain relief from a so-nographically guided injection of steroid into theadjacent iliopsoas bursa [35].

tended field of view sonographic image shows then the greater trochanter. A small bony enthesophyteimus tendon is thickened and hypoechoic. (B) Closeroechoic gluteus minimus tendon (asterisk), with smallarrows). A small amount of anechoic fluid appears inthe deep trochanteric bursa). The overlying gluteusrow).

Fig. 5. Short axis sonographic image of the iliopsoastendon in a patient who has undergone total hipreplacement shows a thickened and ill-defined iliop-soas tendon (white arrow). The black arrow pointsto the pelvic brim.

Fig. 3. Short axis sonographic image of the greatertrochanter shows a hypoechoic full thickness tear ofthe anterior aspect of the gluteus medius tendon(white arrow). The posterior aspect of the tendon(black arrow) is present attaching to the posterioraspect of the lateral facet of the greater trochanter.

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To evaluate suspected snapping of the iliotibialband or gluteus maximus, the patient either laysdecubitus with the affected side up or standsupright, and the transducer is placed transverselyover the lateral aspect of the greater trochanterwhile the patient flexes and extends the hip. Alter-natively, the snapping may occur when the patientrotates the hip internally and externally.

Iliopsoas tendon

Patients who have had hip arthroplasty maydevelop pain in the groin or over the anterior aspectof the hip from impingement of the iliopsoas ten-don against the anterior aspect of the acetabularcup. Sonography can show the direct contact ofthe cup and the tendon, and the tendon may appearenlarged, ill-defined, or hypoechoic, and may havesurrounding or adjacent iliopsoas bursitis (Fig. 5).

Fig. 4. Longitudinal sonographic image of the greatertrochanter shows a torn and retracted gluteus mediustendon (short white arrow points to the tendonedge), and a small amount of hypoechoic fluid atthe bare attachment site (long white arrow). Theoverlying iliotibial band is present (black arrow).

However, in many instances direct impingement isnot confirmed and the tendon looks normal. Sono-graphically guided injection of steroid or anestheticaround the tendon and into the iliopsoas bursa atthe level of the acetabular rim can be diagnosticand therapeutic, but the definitive treatment isiliopsoas tenotomy [36].

Adductor muscles

The adductor muscle group is comprised of theadductor longus, adductor magnus, adductor bre-vis, pectineus, gracilis, and obturator externus[37]. Adductor muscle injuries are most oftenencountered in soccer, hockey, cricket, Australianrules football, and breaststroke swimmers [37–42], and are a common cause of groin pain inthese athletes. The adductor longus is most com-monly affected [33].

The strain can occur at the tendon origin on thesymphysis pubis [43], at the musculotendinousjunction [44,45], and at the distal insertion onthe femur (called thigh splints) [46–48]. Sonographyof the acutely injured adductors may show focalhypoechoic defects or gaps at the musculotendi-nous junction, a hypoechoic acute hematoma,hyperemia with color or power Doppler, or corticalirregularity of the bone at either the symphysispubis attachment or the femoral attachment(Fig. 6) [44–46]. Goh and colleagues [44] reportedsonographically guided aspiration of a hematomawithin a tear of the adductor muscles of the groin,followed by two courses of injection of anestheticand steroid into the tear, 7 weeks apart, with com-plete resolution of groin pain. The chronicallytorn muscle will exhibit decreased bulk andincreased echogenicity from fatty atrophy [48].

Fig. 7. Longitudinal sonographic image at the level ofthe hip shows a partial avulsion of the direct head ofthe rectus femoris muscle with a hypoechoic cleft(open arrow) between the muscle and the anteriorinferior iliac spine (AIIS), and a small fragment ofavulsed echogenic bone (white arrow). The indirecthead of the rectus femoris muscle and femoral headare identified in this image.

Fig. 6. Short axis sonographic image in a patient withleft sided groin pain shows hypoechogenicity of theadductor origin (asterisk) and cortical irregularity(white arrows) of the anterior aspect of the superiorpubic ramus. (Case courtesy of Dr. Levon Nazarian,Philadelphia, PA.)

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Tensor fascia lata

Unilateral enlargement of the tensor fascia lata mayoccur because of degeneration and overuse. In Bassand Connell’s [49] series of 12 patients, all com-plained of anterior groin pain and point tendernessover the anterior iliac crest and all were engaged inathletic activities. Sonography in all of thesepatients showed enlargement of the tensor fascialata with a cone-shaped region of hypoechogenicityat its origin, and a linear anechoic intrasubstancetear of the muscle in three patients. The unilateralenlargement may also mimic a soft tissue mass,prompting imaging evaluation [50]; two cases oftear of the tensor fascia lata reported by Asingerand El-Khoury [51] also presented as soft tissuemasses from retraction of the avulsed muscle.

Rectus femoris muscle

The rectus femoris muscle is the most anterior of thequadriceps group and has two proximal origins fromthe pelvis. The direct head of the rectus femoris mus-cle arises from the anterior inferior iliac spine andgives rise to a superficial aponeurosis and unipen-nate muscle structure, whereas the indirect headoriginates from the supra-acetabular region andgives rise to the central tendon of the muscle witha bipennate muscle structure. This configuration ofouter unipennate fibers and inner bipennate fibersgives a ‘‘muscle within a muscle’’ appearance on axialsonographic images, with the central tendon havingan echogenic linear appearance [52].

Like the hamstring muscles, the rectus femorismuscle is composed mostly of type 2 fibers, crossestwo joints, and has two heads of origin, all of whichmake it susceptible to tear from sports requiringa sudden forceful contraction, either from hip flex-ion or knee extension, such as sprinting or kickinga ball [53]. Tears of the rectus femoris muscle are

more common at the distal musculotendinousjunction near the quadriceps tendon but may alsooccur proximally (Fig. 7).

Bianchi and colleagues [52] described threesonographic patterns of rectus femoris muscleinjury: type 1, a mild partial tear, appearing ashyperechogenicity in the center of the musclecaused by hemorrhagic infiltration, obscuring thecentral hyperechoic central tendon (Fig. 8); type 2,a moderate partial tear, appearing either as mixedhypo- and hyperechogenicity (Fig. 9) or a ‘‘bull’seye’’ configuration with hypoechoic hematomasurrounding the echogenic central tendon and anouter rim of echogenic hemorrhagic infiltration;and type 3, complete musculotendinous disrup-tion, with the echogenic central tendon coursingthrough a large hypoechoic hematoma with retrac-tion of the torn muscle fibers (Fig. 10).

In skeletally immature athletes, forceful flexionof the hip, such as in sprinting or kicking, can causeavulsion of the anterior iliac spine apophysis by thedirect head of the rectus femoris, representinga Salter 1 injury, rather than cause tear of the muscleitself as in adults. Longitudinal scanning over theanterior inferior iliac spine will demonstrate thedisplaced thin echogenic surface of the avulsedapophysis [54].

Hamstrings

The hamstring group comprises the biceps femoris,semimembranosus, and semitendinosus muscles.The long head of the biceps femoris and the semi-membranosus and semitendinosus muscles

Fig. 8. Short axis sonographic image of the rectusfemoris muscle shows a wedge shaped area of fainthyperechogenicity (short white arrows) indicatinghemorrhage adjacent to the echogenic linear centraltendon (long white arrow).

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originate from the ischial tuberosity of the pelvis,and the short head of the biceps femoris originatesfrom the femoral shaft. The distal biceps femoristendon inserts on the fibular head after joiningwith the fibular collateral ligament, the semimem-branosus inserts on the posterior aspect of themedial side of the proximal tibia, and the semite-ndinosus tendon inserts on the anterior aspect ofthe medial side of the proximal tibia as one of thepes anserinus tendons.

Sports that involve sprinting or quick accelera-tion may lead to hamstring injury. In soccer, mosthamstring injuries occur while running, with only7% caused by player-to-player contact [55]. Musclestrain is related to the extreme tensile forces gener-ated during sprinting. Because the forces generatedby the muscle contraction are complex, susceptiblemuscles are those that are composed of a highproportion of type 2 muscle fibers (because theyproduce a more powerful contraction than type 1fibers) and muscles that cross two joints and havemore than one head of origin (eg, the bicepsfemoris) [53]. Muscle fatigue also contributes to in-jury, with 47% of injuries in professional soccerplayers occurring toward the end of each half of

play [55]. Previous hamstring injury is also a riskfactor for repeat injury [55], and older players(>22 years of age) are more often injured thanyounger players (17–22 years of age) [55,56].

The biceps femoris is the most commonly injuredhamstring muscle, followed by the semimembrano-sus, and lastly the semitendinosus [57,58]. In oneseries, 5% of injuries involved more than one mus-cle [57]. Tear of the hamstrings most often involvesthe musculotendinous junction, occurring in 52%to 76% of cases [57–59], followed by the myofas-cial junction of the epimysium in 35% of cases[57,58]. Avulsion of the proximal or distal tendonsthemselves is rare, with 16 cases of proximal tendonavulsion, one case of distal biceps femoris avulsion,and three cases of distal semitendinosus tendonavulsion in a series of 170 patients [58].

The sonographic appearance of muscle injury isthe same as that already described for the rectusfemoris muscle. Intramuscular bleeding caused bymild tearing is hyperechoic. More extensive tearingappears as focal hypoechoic edema, typically adja-cent to the linear echogenic central tendon (themusculotendinous junction), and disruption ofthe pennate architecture of the muscle [57,58].

MR imaging is more sensitive than sonographyfor detecting mild muscle strain because of itsgreater soft tissue contrast [58]; in a series of ham-string injuries imaged with MR imaging and sonog-raphy, the abnormalities always appeared larger onMR imaging because of the greater soft tissuecontrast and consequent better conspicuity of mus-cle edema [57].

Sonography is less accurate than MR imaging fordiagnosing proximal hamstring avulsion, becausethe presence of a mixed echogenicity hematomaand the deep location of the ischial tuberosity, par-ticularly in heavy or muscular patients, can makedetection of the avulsed tendon difficult [58]. Kou-louris and Connell [58] found that MR imagingcorrectly identified acute avulsion from the ischiumin 16 of 16 cases, whereas sonography only diag-nosed 7 of 12 cases.

Fig. 9. Longitudinal ex-tended field of view sono-graphic image of theanterior aspect of the thighshows a partial tear of therectus femoris muscle withan anechoic hematoma(asterisk), linear anechoicinterstitial tearing (arrow),and generalized hypere-choic disruption of the pen-nate appearance caused byinterstitial bleeding.

Fig. 10. Rectus femoris muscle tear. (A) Longitudinal sonographic image of the anterior aspect of the thighshows a complete tear of the rectus femoris muscle at the musculotendinous junction. The proximal and distalextents of the tear are outlined by the asterisks; portions of the torn muscle are demonstrated by the round tailarrows, the straight white arrows point to the central tendon, and the black arrow points to fibrinous materialwithin the tear. (B) Corresponding coronal proton density MR imaging, oriented to match the sonographicimage, shows the high signal intensity hematoma, the torn muscle (round tail arrow), the central tendon(straight white arrows), and the focal fibrinous material (black arrow).

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In addition to the objective demonstration ofmuscle injury that can confirm a clinical diagnosis,both MR imaging and sonography have been usedto predict time to return to activity. In two series,MR imaging showed no abnormality in 18% to31% of patients who had clinical hamstring injury[56,60], and patients who had no imaging evidenceof injury returned to competition sooner than thosewho had demonstrable abnormalities.

In a study of 60 soccer players who had acutehamstring injury clinically, sonography was slightlymore sensitive than MR imaging for detecting strain(75% versus 70%), but the length of the strain onMR imaging had the best statistical correlationwith time to recovery [57]. Similarly, other studieshave found that length and cross-sectional area ofmuscle injury on MR imaging and involvement ofthe central tendon are important prognostic indica-tors for time to recovery [61,62]. In one study ofpatients who had positive MR imaging or sono-graphic examinations, longitudinal length of tearon MR imaging was the best predictor of time toreturn to competition [57]. In a different study,the percentage of abnormal muscle area and vol-ume of muscle injured correlated with the numberof days lost from competition [59]. The risk forrecurrent hamstring injury increases with largersize of initial injury; recurrence risk is more thantwofold if the transverse size of the injury is 55%or more of the muscle or the volume of injury ismore than 21.8 cm3 [63].

Knee and calf

Distal quadriceps tendon rupture

The quadriceps tendon is the conglomeration ofthe distal tendons of the rectus femoris, vastus lat-eralis, vastus intermedius, and vastus medialismuscles, and is a long, broad tendon that inserts

on the anterior aspect of the superior pole of thepatella.

The cause of tears is eccentric contraction of theextensor mechanism, usually caused by stumbling,as the flexing knee tries to extend against the per-son’s weight. The ruptured tendon usually hassome underlying abnormality, such as tendinosusor generalized weakening, caused by a systemicchronic medical condition such as diabetes, chronicrenal failure, rheumatoid arthritis, or chronic ste-roid therapy. Tear is more common in people olderthan 40 years than in teenagers or young adults[64].

Partial tearing usually appears as a hypoechoiccleft in the tendon, and scanning should be per-formed in the long and short axis to determinethe extent of the injury. Rupture is complete discon-tinuity of the tendon (Fig. 11), and longitudinalscanning is useful to assess tendon discontinuityand the amount of retraction. When the torn edgesare apposed to each other, longitudinal scanningwith the knee flexed can distinguish a partial tearfrom a nonretracted rupture [65,66].

Patellar tendinosis and tear

The patellar tendon is the continuation of the quad-riceps tendon, comprised mostly of the rectus fem-oris component, which passes over the anterioraspect of the patella and inserts on the tibial tuber-cle. The normal patellar tendon is less than 75%of the thickness of the quadriceps tendon and hasparallel surfaces.

Patellar tendinosis is seen in adults and mayoccur anywhere along the patellar tendon. Thedevelopment of tendinosis is related to the ageand weight of a person [67]. Histologic analysis oftendon degeneration shows crimping and disorga-nization of collagen fibers and mucinous degenera-tion of collagen. Neovascularization caused by

Fig. 11. Longitudinal ex-tended field of viewsonographic image ofa quadriceps tendon tearshows the ruptured and re-tracted tendon edge (shortwhite arrow) with hypere-choic bone fragment andshadowing (long whitearrow). Anechoic edemaand echogenic hemorrhageare present in the tendongap (asterisk). P, patella.

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angiofibroblastic proliferation may also be present[14]. Sonographically, tendinosis appears as hypoe-choic loss of the normal echogenic fibrillar appear-ance of the tendon and tendon thickening(Fig. 12). Power or color Doppler imaging mayshow hyperemia of neovascularity.

Rupture of the patellar tendon, manifested sono-graphically as discontinuity of the tendon, mostoften occurs at the proximal aspect of the tendon,usually through an area weakened by tendinosisor previous surgery (Fig. 13). Rupture of the tendonat its midportion usually results from a direct blow.Patellar tendon rupture is less common than quad-riceps tendon rupture, tends to occur in youngeradults, and is more common in men than woman.In older adults, the same systemic diseases that arerisk factors for quadriceps tendon tear, namely dia-betes, chronic renal failure, rheumatoid arthritis,and chronic steroid therapy, are also risk factorsfor patellar tendon rupture [68].

Jumper’s knee (patellar tendinitis)

Jumper’s knee refers to a symptomatic focus of tendi-nosis and partial tearing that occurs in the proximalaspect of the patellar tendon, and gets its namebecause it is seen in basketball players, volleyballplayers, and other athletes whose sport requires

Fig. 12. Patellar tendinosis. (A) Longitudinal sonographicened and heterogenously echogenic patellar tendon (blacthe tibial insertion (T). (B) Longitudinal sonographic imagarrows) shows the normal echogenic fibrillar appearance

repetitive forceful extension of the knee [69]. Ina study of 613 elite athletes representing nine sports,the overall prevalence was 14%, with 45% in volley-ball, 32% in basketball, and 0% in cycling [69]. Thisinjury usually occurs in teenagers and young adults,and occurs in the proximal aspect of the tendonbecause the tensile stress transmitted through thetendon is greatest at the patellar insertion.

Pathologically, crimping and mucoid degenera-tion of the collagen fibers and angiofibroblasticproliferation occur, with eventual partial tearing.The term tendinitis is a misnomer because no acuteinflammation is seen histologically [70].

The normal patellar tendon has an echogeniccoarse fibrillar pattern, but in Jumper’s knee thefibrillar appearance is effaced by hypoechogenicityand the tendon is fusiform thickened. However,the cause of pain associated with the sonographicappearance is not well understood because thesegrayscale sonographic findings may be seen inboth symptomatic and asymptomatic individuals,and symptomatic athletes may be sonographicallynormal [71–73]. Conversely, in a study of 134 eliteteenage basketball players, 22% of clinically normaltendons had sonographically abnormal foci [74].Moreover, the grayscale appearances may resolve,persist, or enlarge, without any relation to

image of the patella tendon shows a markedly thick-k arrows), extending from the patellar insertion (P) toe of a normal patellar tendon for comparison (blackand parallel borders.

Fig. 13. Longitudinal ex-tended field of view sono-graphic image of a patellartendon rupture showsa thickened tendon withtendinosis and rupturededges (white arrows arethe proximal tendon edgeand black arrows are thedistal tendon edge), withintervening heterogeneoushypoechoic and echogenicedema and fibrinous mate-rial. P, patella; T, tibia.

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symptoms [75,76]. Nonetheless, asymptomaticathletes who have a hypoechoic focus have a fourtimes greater risk for developing symptoms thanasymptomatic controls [75], and athletes whohave no symptoms and normal sonography haveonly an 8% risk for developing jumper’s knee [77].

Power or color Doppler imaging of the degener-ated tendon may show hyperemia, reflecting angio-fibroblastic proliferation (Fig. 14). The presence ofneovascularity in the degenerated tendon may bethe clue to symptomatology [78,79], but the find-ings are controversial because 8 of 20 symptomaticfoci in one study lacked vascularity on power Dopp-ler imaging [71] and 10 asymptomatic tendons inanother study had both grayscale and Dopplerabnormalities [72].

Osgood-Schlatter diseaseand Sinding-Larsen–Johansson disease

Osgood-Schlatter disease (OSD) and Sinding-Larsen Johansson disease (SLJD) are chronicoveruse injuries seen in sports involving forcefulcontraction of the extensor mechanism, such asencountered in cutting maneuvers and jumping.Whether patella alta, patella infera, or tibial torsionpredisposes to OSD because of altered tensile stress

Fig. 14. Jumper’s knee. (A) Longitudinal sonographic imagfusiform thickening (white arrows) and ill-defined interstitgraphic image with power Doppler imaging shows marke

on the patellar tendon–tibial tubercle apophysealattachment is debated [80].

These abnormalities affect adolescents, before thepatella is completely ossified and before the tibialtubercle apophysis has fused. Girls may be affectedat a slightly younger age than boys. OSD affects thedistal aspect of the patellar tendon, whereas SLJDaffects the proximal aspect of the tendon.

SLJD proximally and OSD distally are caused byrepetitive partial tearing of the tendon and smallavulsions of the cartilaginous attachment of the pa-tellar tendon to the lower pole of the patella andtibial tubercle apophysis, respectively. The smallavulsed cartilage fragments may ossify, and thesmall tendon tears may eventually cause the forma-tion of foci of heterotopic ossification [80–82].

Radiographically, OSD and SLJD show hetero-topic ossification within the patellar tendon, butnormal variations in development of the ossifica-tion centers of the tibial tubercle apophysis andlower pole of the patella may mimic heterotopicossification. The distinguishing feature of theseconditions from normal variations is the presenceof tendon thickening and soft tissue swelling andthe clinical presence of pain and tenderness in theaffected region.

e of the proximal aspect of the patella tendon showsial hypoechogenicity (asterisk). (B) Longitudinal sono-d internal and peritendinous hyperemia.

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Sonography of OSD and SLJD shows the thick-ened tendon with loss of the echogenic fibrillarappearance. Foci of heterotopic ossification willhave echogenic surfaces with varying amounts ofposterior acoustic shadowing. Distension of thedeep infrapatellar bursa is sometimes present andappears as a hypoechoic collection deep to the dis-tal aspect of the tendon (Fig. 15).

The posterolateral corner

The posterolateral corner of the knee is stabilized bya complex combination of ligaments and tendons.Static stabilization is provided by the fibular collat-eral ligament, arcuate ligament, popliteus tendon,popliteofibular ligament, and fabellofibular liga-ment. Dynamic stabilization is provided by thepopliteus, biceps femoris, and lateral gastrocne-mius muscles. The distal tendon of the biceps fem-oris and the fibular collateral ligament blendtogether at their insertion on the fibular head toform the conjoined tendon [83–85]. Of these stabi-lizers, the fibular collateral ligament, popliteofibu-lar ligament, and popliteus muscle and tendonare the most important [86].

These structures have been identified sonographi-cally in cadavers [87], but the efficacy of sonographyfor evaluating the acutely injured posterolateralstructures has not been determined. Moreover, thesestructures are usually part of a larger injury patternresulting from a combination of hyperextensionwith either varus force or external rotation of thetibia that also includes the anterior and posteriorcruciate ligaments, the medial collateral ligament,and menisci [83,84,86,88].

Calf

The plantaris, gastrocnemius, and soleus musclesare located in the superficial posterior compartment

Fig. 15. Longitudinal sonographic image of the distalaspect of the patella tendon in a patient with Os-good-Schlatter disease shows a normal appearing dis-tal patellar tendon (black arrows) that is thickenedand hypoechoic distally and contains an echogenicfocus of heterotopic ossification (large black arrow).T, tibia.

of the leg, and constitute the triceps surae. The gas-trocnemius muscle is the most superficial; it hasmedial and lateral heads arising from the posterioraspects of the respective femoral condyles andbecomes tendinous approximately midway downthe leg, merging with the fibers of the soleus muscleto become the Achilles tendon. The soleus muscle isdeep to the gastrocnemius and arises from the pos-terior aspects of the proximal tibia and fibula.

The plantaris muscle arises from the lateral fem-oral condyle, superior and medial to the origin ofthe lateral head of the gastrocnemius muscle; theplantaris muscle belly is short and small, and tapersto a long tendon at the level of the proximal tibia.The plantaris tendon courses medially, runningbetween the medial head of the gastrocnemiusmuscle and soleus muscle, and along the medialaspect of the Achilles tendon, to insert on the calca-neus. Thus, the gastrocnemius and plantaris mus-cles span the knee and ankle joints. The plantarismuscle is anatomically inconstant, being absent in7% to 20% of people [89].

Tennis leg refers to tear of the medial gastrocne-mius muscle or plantaris muscle. Both muscles arecomposed of type 2 (fast) muscle fibers and crosstwo joints, factors that increase the risk for injury[53,89]. The actions of dorsiflexion of the footand extension of the knee can cause overstretchingof either muscle [90]. Patients report acute sponta-neous pain in the calf, often associated with a pop-ping sensation. In one series of 30 patients,symptoms occurred while playing soccer in 22 casesand during tennis in 8 [91]. However, injury mayalso occur during routine activity.

Tennis leg most often affects middle-aged people,usually men, with an average age of 39 years in oneseries [90] and 45 years in another [89], but its prev-alence is unknown. Although injury of either thegastrocnemius or plantaris muscles may producesymptoms that are clinically regarded as tennisleg, the gastrocnemius muscle is usually affected.In a series of 141 patients who had clinical tennisleg examined sonographically, 94 had injury ofthe medial head of the gastrocnemius muscle, 2had plantaris tendon ruptures, and 1 had tear ofthe soleus muscle [89].

Injury of the medial head of the gastrocnemiusmuscle may be either partial tear or complete ruptureand occurs at the musculotendinous junction. Com-plete rupture was more common in the two seriesreported by Kwak and colleagues [90,91], whereaspartial tear was more common in the series of 65patients reported by Bianchi and colleagues [92].

Partial tear of the medial head of the gastrocne-mius muscle appears as focal disruption of the pen-nate appearance of the musculotendinous junctionof the muscle (Fig. 16) or as anechoic edema or

Fig. 16. Longitudinal ex-tended field of view sono-graphic image of the calfshows a tear of the gastroc-nemius muscle with hetero-geneous disruption of thenormal pennate appear-ance (white arrows) anda distal area of echogenic-ity (black arrow) represent-ing interstitial blood.

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hematoma tracking along the central tendon(Fig. 17), whereas rupture appears as complete dis-continuity [89–92]. The transverse plane is best fordistinguishing the two. An initially hypoechoichematoma is often present between the gastrocne-mius and soleus muscles, which becomes echogen-ic over 1 to 2 weeks [90,92]. Kwak and colleagues[90,91] also report the development of echogenicfibrous tissue between the torn muscle and tendonat 2 to 4 weeks after injury, as part of the healingprocess, with eventual bridging of the tear. Bianchiand colleagues noted [92] similar hyperechoic scarin the patients who were rescanned sonographically1 year or more after the initial injury.

Injury of the plantaris may affect the muscle,musculotendinous junction, or the tendon itself[93,94]. In a series of 15 patients, Helms and col-leagues [93] found that 3 had rupture at the muscu-lotendinous junction and the remainder hadmuscle strains; 10 of the patients who had plantarismuscle strains also had anterior cruciate ligamenttears. Plantaris rupture appears as tendinous dis-continuity, with retraction of the echogenic tendon[89,94]. A large hypoechoic hematoma is oftenpresent between the medial head of the gastrocne-mius and soleus muscles.

Ankle

The ankle is often the most commonly injuredregion of the lower extremity, usually from an inver-sion injury resulting in a twisted or sprained ankleconsisting of ligamentous injury [3]. In contrast,the Achilles, flexor, and peroneal tendons are sub-ject to overuse and may become symptomatic

Fig. 17. Longitudinal extended field of view sonographicmusculotendinous tear of the gastrocnemius muscle withtral tendon (black arrow).

from tendinosis; tendinosis in turn predisposes topartial tear and rupture [95,96].

Achilles tendon

The Achilles tendon is formed by the tendinouscontributions of the gastrocnemius and soleus mus-cles. It is a long broad tendon, inserting on the pos-terior aspect of the calcaneus, and has the greatesttensile strength of any human tendon [97]. Achillesinjury is usually the result of overuse, typicallyencountered in athletic activities that involvechronic repetitive tensile forces such as runningand jumping [98], but numerous contributing fac-tors have been described including anatomic varia-tions such as mild limb length discrepancy andhyperpronation and varus alignment of the affectedfoot, calf muscle weakness and fatigue, and variouserrors in training [99].

Although many terms have been used to describeAchilles abnormalities, the term tendinopathy isa clinical term describing pain, swelling, and resul-tant decreased athletic capability [99,100], whereastendinosis refers to the structural changes of degener-ation seen histologically or with imaging [99].

The processes of tendinopathy and tendinosiscan be mutually exclusive. In 83 patients who hadclinical tendinopathy, tendinous changes wereseen sonographically in 29 (35%), with the remain-ing symptomatic cases showing no intratendinouschanges; 18 asymptomatic tendons showed sono-graphic abnormalities [101]. Similarly, in a differentstudy of 45 patients who had clinical tendinopathy,20 of 57 clinically abnormal tendons were normalsonographically, whereas 9 of 28 clinically normal

image through the calf shows a large full-thicknessan anechoic hematoma (asterisk) adjacent to the cen-

Fig. 18. Longitudinal ex-tended field of view sono-graphic image of theAchilles tendon shows ten-dinosis manifest by fusi-form thickening (whitearrows) of the tendon andinternal hypoechogenicity.

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tendons were sonographically abnormal [102].Although some studies have shown that symptom-atic patients who have normal sonography havea significantly better clinical outcome than patientswho have sonographic abnormalities [103,104],Khan and colleagues [102] found the severity ofthe ultrasound findings at baseline was not associ-ated with clinical outcome 1 year later.

Tendinosis and tears usually involve the proximaltwo thirds of the tendon [105]. Insertional tendino-sis, defined as degeneration occurring in the distalthird of the tendon, accounts for 8% to 25% ofcases of Achilles tendinopathy [105,106] and tendsto occur in older, less-active, or heavier individuals[106].

Tendinosis (intrasubstance degeneration)appears as focal hypoechogenicity replacing thenormal echogenic fibrillar architecture, usually butnot always associated with focal enlargement ofthe tendon (Fig. 18), and foci of echogenic calcifi-cation may be present in the tendon (Fig. 19).Intrasubstance partial tear is usually a more well-defined hypoechoic cleft or focus (Fig. 20), but dis-tinction between tendinosis and intrasubstancepartial tear can be difficult [107]. Power or colorDoppler imaging may show neovascularity fromdegenerative angiofibroblastic proliferation(Fig. 21). Abnormality of the paratenon has beendescribed as an ill-defined or fluid-like rim aroundthe tendon but is not reliably shown [107].

Rupture of the Achilles tendon appears as com-plete disruption of the fibrillar echogenic appear-ance of the tendon with or without retraction(Fig. 22). In acute ruptures, heterogeneous echo-genic edema and hemorrhage are often presentbetween the torn tendon edges. Sensitivity of ultra-sound for diagnosing Achilles tendon rupture is

96% to 100% and specificity is 83% to 100%[107,108].

Features associated with acute rupture are tendonretraction; posterior acoustic shadowing caused byrefractive shadowing of the sound beam by the dis-rupted and curled tendon edges; tendon thinness;herniation of Kager’s fat into the tendon gap; andvisualization of the plantaris tendon (along themedial aspect of the Achilles tendon), which is usu-ally silhouetted by the adjacent Achilles [108].Healed ruptures usually appear as a focally thick-ened region with variable presence of fiber distor-tion, hypoechogenicity, and calcification [109,110].

The clinical significance of the vascularity in theAchilles tendon, shown either with color or powerDoppler sonography, is controversial. Some serieshave shown the presence of vascularity in symp-tomatic tendons but not in asymptomatic tendons[111,112], and have reported therapeutic pain reliefafter sonographically guided sclerotherapy of thevessels [113,114]. However, other investigatorshave found vascularity in asymptomatic individuals[10,115]. Boesen and colleagues [10,115] haveshown increased vascularity in the Achilles tendonafter exercise, even in asymptomatic people,whereas other investigators have shown a correla-tion of vascularity with increasing thickness of thetendon [116,117], perhaps reflecting a greater de-gree of degeneration.

Flexor tendons

The posterior tibial tendon (PTT), flexor digitorumlongus tendon, and flexor hallucis longus tendonare contained within the tibial tunnel in the poster-omedial aspect of the ankle. The PTT is normallyalmost twice the diameter of the flexor digitorumlongus tendon, and both may normally have

Fig. 19. Longitudinal ex-tended field of view sono-graphic image of Achillestendinosis shows fusiformthickening with internalechogenic calcification(arrows).

Fig. 20. Short-axis sonographic image of the Achillestendon shows a focal well-defined anechoic tear(white arrow), adjacent to an ill-defined and heterog-enous region of tendinosis (black arrows).

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a thin rind of surrounding hypoechoic fluid[118,119].

The PTT is the most commonly abnormal flexortendon, usually representing chronic degenerationand eventual tearing, occurring in middle- to old-er-aged adults and more often affecting women.Because the PTT is the major stabilizer of the medialcolumn of the foot, dysfunction of the tendon

Fig. 21. Achilles insertional tendinosis with neovascularization of the Achilles tendon shows abnormal fusiform thichypoechogenicity (black arrows). (B) Longitudinal sonograison shows the normal echogenic fibrillar and straightpower Doppler image of the patient’s affected side (samthe area of tendinosis.

presents clinically with medial ankle pain, loss ofthe medial arch of the foot, hindfoot valgus, andforefoot abduction [120,121].

The sonographic appearance of PTT tendinosis isthickening of the tendon with ill-defined hypoe-choic foci replacing the normal echogenic fibrillarappearance; linear well-defined hypoechoic focimay represent interstitial tears, whereas globularfoci may represent focal mucoid degeneration.Hypoechoic fluid may be present surrounding thetendon, or the tendon sheath may be thickened(Figs. 23–25). Extensive partial tears may causethinning of the tendon, and rupture is shown ascomplete tendinous discontinuity [122,123].

Using MR imaging as the gold standard, Premku-mar and colleagues [123] found that ultrasoundhad 80% sensitivity and 90% specificity for detect-ing tendinous abnormalities, and 90% sensitivityand 80% specificity for peritendinous changessuch as fluid in the tendon sheath and hyperemiaof the tendon sheath on Doppler imaging. MRimaging, however, may not be an accurate goldstandard, because Nallamshetty and colleagues[122] found a 77% concordance between MR imag-ing and ultrasound for evaluating PTT pathology,and the five discordant cases were more in

tion. (A) Longitudinal sonographic image of the inser-kening (white arrows) with a focal area of interstitialphic image of a normal tendon insertion for compar-

appearance of the Achilles tendon. (C) Longitudinale tendon as image A) shows neovascularization in

Fig. 22. Longitudinal ex-tended field of view sono-graphic image of anAchilles tendon ruptureshows the torn offset edgesof the ruptured tendon(white arrows). The distalaspect of the tendon ismarkedly thickened andhypoechoic.

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agreement clinically with ultrasound than the MRimaging interpretation. In a study of surgically cre-ated PTT tears in cadavers, Gerling and colleagues[120] found that both imaging modalities had72% accuracy, with a positive predictive value of88% for MR imaging and 92% for ultrasound.

Lim and colleagues [124] described fluid in thePTT sheath, a tibial spur on the distal posteriorouter margin of the medial malleolus, unroofingof the talar head on axial images resulting fromforefoot abduction and hindfoot valgus, and tibialmarrow edema as secondary finding of PTT dys-function on MR imaging. However, caution shouldbe exercised, because a thin rind of fluid may nor-mally surround the PTT [118], tibial spurring hashigh specificity but low sensitivity [124], reactivemarrow edema cannot be detected sonographically,and unroofing of the talar head has not been quan-tified sonographically. Moreover, the structuralchanges in foot alignment that result from PTT dys-function are not solely from an abnormality of thePTT itself; the superomedial and inferomedial com-ponents of the spring ligament complex and talo-calcaneal interosseous ligament of the sinus tarsiare also abnormal [125], but the ability of sonogra-phy to show these ligaments has not been assessed.

Fig. 23. Posterior tibial tendinosis and tenosynovitis. (A) Shposterior tibial tendon (white arrow) and an adjacent nothin normal amount of anechoic fluid is present. (B) Shorshows an area of ill-defined hypoechogenicity (long whitear, and a thick rim of surrounding anechoic fluid (short

Dislocation of the PTT is a traumatic occurrencerather than a degenerative process, caused by frankavulsion or stripping of the flexor retinaculum fromthe medial malleolus, allowing the tendon tosublux anteriorly [126]. The stripped or rupturedretinaculum and displaced PTT can be shown sono-graphically. Sometimes dynamic scanning in thetransverse plane during dorsiflexion and plantarflexion of the foot is necessary to show the unstableposition of the tendon.

The painful flexor hallucis longus tendon hasbeen termed dancer’s tendinitis [127], referring tothe posterior ankle pain experienced by ballerinasfrom repetitive hyperplantarflexion of the foot inthe en pointe position. This repetitive positioningcan eventually lead to stenosing tenosynovitis ofthe flexor hallucis longus as it passes behind thetalus. Typical patients with flexor hallucis longuspain are ballerinas [128], with the left foot morecommonly affected than the right because mostturns are to the right, requiring pivoting on theleft foot [127], but adults of any age and gendermay develop posterior ankle pain that is not alwaysassociated with sports [129,130].

Clinically, patients who have flexor hallucis lon-gus pain experience tenderness to palpation along

ort-axis sonographic image shows a normal echogenicrmal flexor digitorum longus tendon (black arrow). At-axis sonographic image of posterior tibial tendinosiste arrow), perhaps with a linear anechoic interstitialwhite arrow) in the tendon sheath.

Fig. 24. Short-axis sonographic image of posterior tib-ial tendon shows tendinosis and a linear hypoechoicinterstitial split tear (short white arrow). The tendonis surrounded by a markedly thickened tendon sheath(long white arrows).

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the tendon at the posterior aspect of the ankle andpain throughout the entire range of motion [129],compared with patients who have posterior ankleimpingement caused by an os trigonum or largeposterior talar process, who experience pain onlyin plantar flexion [127,129]. Because the flexor hal-lucis longus courses under the sustentaculum taliand is adjacent to the posterior tibial nerve in thetarsal tunnel, patients may present with medialankle pain or heel pain mimicking plantar fasciitis[129]. Trigger-toe deformity of the hallux may bepresent because of nodular tenosynovitis prevent-ing smooth gliding of the tendon [130]. In a com-parison of two cohorts with flexor hallucis longustenosynovitis, Sammarco and Cooper [130] foundthat dancers experienced symptoms three timeslonger than nondancers and more than twice asmany interstitial tendon tears.

Sonographically, the affected tendon may looknormal, or may be thickened with heterogeneousechogenicity representing degeneration or interstitial

tears and have surrounding hypoechoic fluid fromtenosynovitis. The fluid may be focal, mimickinga cyst because of the focal stenosing tenosynovitis[130]. The tendon sheath may also be thickenedbecause of chronic scar (Fig. 26). Sonographicallyguided injection of the flexor hallucis longustendon sheath has recently been described [131],which has the advantage of directly visualizing thetendon compared with fluoroscopically guidedtenography.

Peroneal tendons

The peroneus longus and brevis tendons are locatedin the fibular groove in the posterior aspect of thelateral malleolus and are held in place by the supe-rior peroneal retinaculum. At the level of the lateralmalleolus, they are ensheathed in a common syno-vium but are invested in their own synovial sheathsdistal to the malleolus. They are dynamic stabilizersof the lateral side of the ankle and are pronators andplantar flexors of the foot; the peroneus brevis ten-don attaches to the base of the fifth metatarsal, andthe peroneus longus tendon crosses under thecuboid and attaches to the first metatarsal andmedial cuneiform.

These tendons are subject to longitudinal splittears and anterior subluxation, two conditionsthat are often associated. Trauma, such as an inver-sion injury, can rupture or strip the superior pero-neal retinaculum from its fibular attachment,allowing the tendons to sublux over the posterolat-eral margin of the fibula. The peroneus brevistendon is more often involved than the longus ten-don [132,133] because it is anterior in the fibulargroove; repetitive subluxation of the brevis tendon,pressed against the malleolus by the longus tendon,acts like a saw to cause a longitudinal split tear ofthe brevis. Transverse sonographic images at thelevel of the malleolus show the split tear as twosmall pieces of brevis tendon with the large pero-neus longus tendon in between (Fig. 27) [132].

Fig. 25. Longitudinal sono-graphic image of posteriortibial tendinosis showsa thickened tendon (whitearrows) and an area ofinterstitial degeneration(asterisk).

Fig. 26. Flexor hallucis longus tendinosis and scar. (A) Longitudinal sonographic image at the level of the hind-foot shows the flexor hallucis longus tendon (white arrows), with adjacent thick hypoechoic scar (black arrows).(B) Short axis sonographic power Doppler image shows the echogenic tendon (white arrow) surrounded by thickscar (black arrow). No hyperemia is present.

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Subluxation may be evident at rest, but occa-sionally dynamic scanning as the foot is dorsi-flexed and everted [132,133] is necessary to showthe peroneal subluxation. Correlation with clinicalsymptoms is important, however, because up to20% of asymptomatic people will exhibit peronealsubluxation [132]. Nontraumatic causes of sublux-ation include a hypoplastic fibular groove andcongenital absence of the superior peroneal reti-naculum [133].

Tears of the peroneus longus tendon are less com-mon than tears of the brevis tendon [134,135]. Thelongus usually tears at the level of the lateral mal-leolus but may rupture in the midfoot as it changes

Fig. 27. Peroneus brevis tendon split tear. (A) Short axis sona hypoechoic longitudinal split tear (round tail arrow) c(straight white arrows), with the intervening peroneus lT2-weighted MR image in this same patient shows the splwith the intervening peroneus longus tendon (black arro

direction at the peroneal groove of the cuboid tocross under the foot. This rupture can occur as a re-sult of inversion injury, strenuous activity in theunconditioned athlete, and systemic disease [136].Sonographic demonstration of a fragmented os per-oneum, with more than 6 mm of distraction of thefragments and hypoechoic in the fragment gap,indicates tendon rupture [136].

In a prospective study of sonography’s ability tocorrectly identify tears of the peroneal tendons,Grant and colleagues [137] reported 100% sensitiv-ity, 85% specificity, and 90% accuracy for diagnos-ing partial and complete tears, using surgery asthe gold standard.

ographic image through the peroneal tendons showsleaving the peroneus brevis tendon into two piecesongus tendon (black arrow). (B) Axial fat suppressedit pieces of the peroneus brevis tendon (white arrows)w).

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Summary

The muscles and tendons of the lower extremity arecommonly injured as a result of sports, chronicoveruse, and systemic diseases. Sonography is wellsuited to evaluating these structures, providinghigh-resolution images and the dynamic ability toevaluate snapping tendons and fascial herniation,and guide percutaneous intervention.

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