Authors:Kelvin Chew, MDKathryn J. Stevens, MDTyng-Guey Wang, MDMichael Fredericson, MDHenry L. Lew, MD, PhD

Affiliations:From the Sports Medicine Center,Department of Orthopaedic Surgery,Alexandra Hospital, Singapore (KC);Department of Radiology, StanfordUniversity School of Medicine, PaloAlto, California (KJS); Department ofPhysical Medicine and Rehabilitation,National Taiwan University Hospital,School of Medicine, National TaiwanUniversity, Taipei, Taiwan (T-GW);Division of Physical Medicine andRehabilitation, Department ofOrthopaedic Surgery, StanfordUniversity School of Medicine, PaloAlto, California (MF); Division ofPhysical Medicine and Rehabilitation,Stanford University School ofMedicine/VA Palo Alto Health CareSystem, Palo Alto, California (HLL).

Correspondence:All correspondence and requests forreprints should be addressed toHenry L. Lew, MD, PhD, PolytraumaRehabilitation Center, VAPAHCS,PM&R Service, MS-B117, 3801Miranda Avenue, Palo Alto, CA 94304.

0894-9115/08/8703-0238/0American Journal of PhysicalMedicine & RehabilitationCopyright © 2008 by LippincottWilliams & Wilkins

DOI: 10.1097/PHM.0b013e31816198c2

Introduction to DiagnosticMusculoskeletal UltrasoundPart 2: Examination of the Lower Limb

ABSTRACT

Chew K, Stevens KJ, Wang T-G, Fredericson M, Lew HL: Introduction todiagnostic musculoskeletal ultrasound: Part 2: examination of the lower limb.Am J Phys Med Rehabil 2008;87:238–248.

This is the second of two articles focusing on ultrasound examination of muscu-loskeletal components of the upper and lower limbs. Treatment of musculoskel-etal injuries is based on establishing an accurate diagnosis. No one would disputethat a good history and physical examination by a competent clinician can helpachieve that in the majority of cases. However, musculoskeletal imaging is also anessential adjunct in the work-up of many musculoskeletal disorders. This articledescribes the ultrasound examination of the lower limb in terms of anatomicstructure. Normal and pathologic ultrasound features of these structures, includ-ing muscles, tendons, ligaments, bursae, and other soft tissues of the lower limb,will be described by reviewing several representative pathologies commonly seenin musculoskeletal medicine.

Key Words: Musculoskeletal, Ultrasound, Lower Limb

Although magnetic resonance imaging remains one of the main diagnosticimaging modalities for evaluating joint pathology worldwide, there are a num-ber of useful applications and advantages of diagnostic ultrasound in theassessment of musculoskeletal pathology. Ultrasonography (U/S) may be used toassess superficial tendons and ligaments that traverse a joint. It can demon-strate the presence and characteristics of joint effusions, bursae, or cysts, and italso can detect loose bodies in joints. The advantages lie in the cost-efficiency,shorter examination time, and the ability for real-time and dynamic imaging. Itsportability allows one to perform imaging of the anatomic structure in questionand to perform rapid side-to-side comparisons. However, the operator depen-dence and long learning curve of U/S are its major drawbacks. Commonterminologies used in this article are shown in Table 1.

U/S APPEARANCE OF LOWER-LIMB MUSCLE PATHOLOGYMuscle strains of the lower limb are commonly seen in musculoskeletal

medicine, and diagnostic U/S can be very helpful in evaluating the severityof the intramuscular disruption. The initial extent of muscle injury anddegree of separation of the margins of the tear are good predictors of

238 Am. J. Phys. Med. Rehabil. ● Vol. 87, No. 3

INVITED REVIEW

Ultrasound

recovery and return to normal function.1 U/S canbe helpful in predicting the expected recoveryperiod and is ideal for serial assessment todocument muscle healing and recovery.1 Theamount of intramuscular scar formation is in-versely proportional to the ability of a muscle toproduce tension, and it is proportional to the riskof recurrent injury.1

Acute muscle injury can be caused by con-tusion from direct contact force or indirectlyfrom eccentric overstretching of the muscle fi-bers. The muscle lesions from these injuries maybe classified according to their location in themuscle mass. Intramuscular lesions occur in theinterior of the muscle, whereas muscle-boundarylesions occur at the muscle–fascia or muscle–tendon interface.1

QUADRICEPS MUSCLE INJURYThe rectus femoris is the most commonly

affected muscle of the quadriceps mechanism in

strain injuries.2 Pain can be elicited with resistedhip flexion, passive hip extension, resisted kneeextension, or passive knee flexion. Figure 1 illus-trates the normal ultrasound appearance of thequadriceps muscle. Microscopically, a normalmuscle consists of hypoechoic muscle fibersgrouped into bundles or fascicles, enveloped inconnective tissue called the epimysium. Thesefascicles are also grouped and enveloped by con-nective tissue called the perimysium or intra-muscular septa, which seems relatively hypere-choic on ultrasound. The muscles are theninvested by an echogenic fascial plane that sep-arates different muscles, known as the epimy-sium or intermuscular septum. In the longitudi-nal plane, ultrasound of the rectus femoris andthe vastus intermedius muscles demonstratesmultiple parallel echogenic striae, separated byhypoechoic muscle fascicles.1 In the transverseplane, the muscle fibers appear hypoechoic, withthe intervening intramuscular septa seen as hy-

TABLE 1 Terminology in musculoskeletal ultrasound

Term Definition

Echogenicity Capacity of a structure in the path of an ultrasound beam to reflect back sound wavesHyperechoic The structure examined in the ultrasound image shows a high reflective pattern, appearing

brighter than the surrounding tissueIsoechoic The structure demonstrates the same echogenicity as the surrounding soft tissuesHypoechoic The structure examined in the ultrasound image shows a low reflective pattern, manifesting

as an area where the echoes are not as bright as the surrounding tissueAnechoic The image of the structure shows no internal echoes, for instance, simple fluidLongitudinal Scan is lengthwise and parallel to the long axis of the structure, organ, or body partTransverse Scan is crosswise and at right angles to the long axis of the structure, organ, or body part

FIGURE 1 Normal quadriceps muscle. A, Longitudinal sonogram showing intramuscular septations (arrow),seen as hyperechoic lines separating hypoechoic muscle bundles. B, Transverse sonogram showingthe intramuscular septations (arrow) as hyperechoic dots on a hypoechoic background. VI, vastusintermedius; RF, rectus femoris; F, femur.

March 2008 Musculoskeletal Diagnostic Ultrasound 239

perechoic dots producing the so-called “starrynight” appearance. The rectus femoris and thevastus intermedius muscles are separated by themarkedly hyperechoic intermuscular septa.1

The ultrasound features of muscle strainsvary with the grade of injury and are summarizedin Table 2. Grade 1 muscle strains consist oftearing of only a few muscle fibers and oftenseem normal on ultrasound. However, the mus-cle may demonstrate small areas of focal disrup-tion or increased echogenicity attributable toperifascial fluid build-up.3 These minor strainsoften recover completely with conservative treat-ment, with no loss of muscle strength or func-tion. Grade 2 muscle strains are larger partial

tears that are usually centered at the myotendi-nous junction, manifested by disruption of theechogenic parallel striae of the muscle with anassociated fluid collection. The features can oftenbe accentuated with active muscle contraction,2

as in the example shown in Figure 2. Grade 2strains often result in pain and loss of function.

A complete muscle tear with retraction ofmuscle fibers surrounded by hypoechoic hema-toma is the characteristic appearance of a grade 3muscle injury,4 as illustrated in Figure 3. Markedrefraction artifacts at the retracted edges may alsobe present. Surgery may be indicated, becausethese injuries can result in muscle retraction andatrophy.

FIGURE 2 Grade 2 vastus intermedius intramuscular tear. A, Longitudinal sonogram showing a largehypoechoic fluid (arrow) with very irregular borders within the substance of the muscle. B,Transverse sonogram depicting hypoechoic fluid (arrow) surrounded by the irregular margins ofthe torn muscle. C, T2-weighted sagittal magnetic resonance image of the anterior quadricepsshowing a large hematoma with high T2 signal intensity (arrow) within the substance of thevastus intermedius, with extensive edema in the remainder of the muscle belly. VI, vastusintermedius; RF, rectus femoris.

TABLE 2 Classification of muscle strains

Pathological Description Ultrasound Appearance

Grade 1 muscle strain Strain injury with no macroscopictissue disruption

Normal appearance; muscle may have anincreased echogenicity attributable toperifascial fluid build-up

Grade 2 muscle strain Partial thickness tear with associatedpartial loss of muscle strength

Disruption of echogenic parallel striae ofthe muscle with associated fluidcollection

Grade 3 muscle strain Full thickness tear with completeloss of muscle function, which may beassociated with retraction ofruptured muscle ends

Complete disruption with retraction ofmuscle fibers surrounded by hypoechoichematoma

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GASTROCNEMIUS MUSCLE INJURYIn the calf, the gastrocnemius muscle is

more commonly injured than the soleus. It iscommonly termed the tennis leg. It is theorizedthat because this biarthrodial muscle extendsacross the knee and ankle, the gastrocnemius ismore susceptible to injury than the uniarthro-dial soleus muscle.5

Figure 4 is a longitudinal ultrasound scan ofthe calf, showing a tear of the medial gastrocne-mius muscle distally. There is a hypoechoic hema-toma around the myotendinous junction of themedial gastrocnemius distally as it tapers into theAchilles tendon.

MYOSITIS OSSIFICANSMysositis ossificans is a rare complication of

muscle injury; it refers to heterotopic bone forma-tion within muscle and other soft tissues that mayoccur after trauma or prolonged immobilization.6

This condition presents with swelling, erythema,and joint stiffness of the affected limb. With U/S,peripheral calcification can be detected before thecalcification becomes visible on plain radiographs.7

In the early phase, myositis ossificans appears as ahypoechoic mass with peripheral echogenic mate-rial and well-preserved surrounding soft-tissueplanes.8 In the late phase, the coarse calcificationscast distinct posterior acoustic shadows, as de-picted in Figure 5.8 Though these features aretypical of myositis ossificans, care should be takennot to confound this with the differential diagnosisof ossifying sarcomas, and advanced imaging maybe necessary.

U/S APPEARANCE OF THE TENDONINJURIES OF THE LOWER LIMB

Tendons are recognized by parallel and finefibrillar patterns on U/S in the longitudinal plane.The parallel fascicles of collagen fibers producehyperechoic lines, with the interfascicular groundsubstance appearing as anechoic lines in between.9

In the transverse plane, tendons appear as round oroval hyperechoic structures. Figure 6 is the longi-tudinal sonogram of a normal patellar tendon withparallel hyperechoic fibrillar lines.

A characteristic feature of tendon and ligamentsonography is anisotropy, where the echogenicityof the structure changes depending on the angu-lation of the ultrasound beam. The structure seemshyperechoic when the beam is perpendicular to thetendon, but it becomes hypoechoic when the beamis directed obliquely.10 This can cause overdiagno-sis of tendon pathology when anisotropy is notrecognized as a confounding factor. More recently,compound imaging or cross-beam imaging havebeen introduced by ultrasound manufacturers toovercome these anisotropy artifacts.

PATELLAR TENDINOSISThe terms tendinosis or tendinopathy have

superseded the term tendonitis as studies haveshown that active inflammation is not consistentlypresent in painful pathology involving the ten-dons.11 Tendinopathy may indicate either tendino-sis, which is a degenerative condition of the tendon

FIGURE 3 Large biceps femoris (BF) intramuscular tear. A, Longitudinal sonogram (extended field of view)showing a large defect occupied by hematoma (arrow) in the substance of the biceps femoris. B,Transverse sonogram depicting a well-circumscribed hematoma within the muscle.

FIGURE 4 Longitudinal sonogram of the medialbelly of the gastrocnemius. Large hema-toma (arrow) is seen adjacent to the myo-tendinous junction.

March 2008 Musculoskeletal Diagnostic Ultrasound 241

attributable to chronically accumulated small-scaleoveruse injury to tendon fibrils, or tendonitis,which is an actively inflamed tendon often associ-ated with an acute injury. Patellar tendinosis is arelatively common cause of anterior knee pain.Tendinosis on ultrasound may manifest as eitherfocal or diffuse thickening of the patellar tendon,with poorly demarcated regions of hypoechogenic-ity corresponding to intrasubstance mucoid degen-eration.12 In chronic, advanced cases, there mayalso be bony spurring of the inferior pole of thepatella, and associated nodularity and calcificationwithin the tendon, particularly adjacent to the car-tilaginous insertion.9,13,14 Figure 7 is a longitudi-nal sonogram of proximal patellar tendinosis(jumper’s knee) with thickening and poorly demar-cated areas of hypoechogenicity. Figure 8 depictscalcific patellar tendinopathy demonstrating focalechogenic calcific foci with associated posterioracoustic shadowing.

Flexing the knee slightly by putting a towelroll under it will stretch out the patellar tendon tofacilitate ultrasound examination, and this willhelp minimize tendon anisotropy. Graded com-pression and assessment of the patellar tendon

during flexion and extension of the knee are ex-tremely helpful for differentiating between partialand complete tendon tears.

TIBIALIS POSTERIOR TENDINOSISTibialis posterior tendon disorders are a com-

mon cause of medial ankle pain. Contributory fac-tors in the pathogenesis of tibialis posterior dys-function include degeneration of the tendon in thearea of relative hypovascularity just posterior anddistal to the medial malleolus and a symptomaticaccessory navicular bone.15 The histologic appear-ance is characterized by mucoid degeneration, dis-ruption of the linear orientation of fibers, and theabsence of inflammation.16 Tibialis posterior dys-function may result in increased forefoot abduc-tion, calcaneal valgus, midfoot collapse, and asso-ciated contracture of the Achilles tendon.17 Theremay be difficulty with ankle inversion and single-leg heel raise. The ultrasound features of chronictendinosis are characterized by enlargement orthickening of the tendon, loss of normal fibrillarechotexture, and loss of definition of the tendonmargins.18 There may also be associated degener-ative intrasubstance tearing of the tendon. Thetibialis posterior tendon is surrounded by a syno-vial sheath, and excess tenosynovial fluid may bepresent, which appears as a hypoechoic ringaround the tendon in the transverse view. Thepresence of irregular echogenic structures withinthe sheath is consistent with synovial proliferation.Some of these features are seen in Figure 9.

ACHILLES TENDON INJURYAchilles tendinosis is an overuse injury com-

monly classified as either noninsertional or in-sertional. Noninsertional tendinosis of the Achil-les tendon can range from localized inflammation ofthe paratenon to tendon degeneration.19 Inser-tional tendinosis is commonly associated with aHaglund deformity, which is a bony prominence of

FIGURE 6 Longitudinal sonogram of normal echo-genic patellar tendon (arrows). Pat, patella.

FIGURE 5 Myositis ossificans. (A) Longitudinal and (B) transverse sonogram of the quadriceps muscle,depicting early intramuscular calcifications (arrow) with associated posterior acoustic shadow-ing (open arrow).

242 Chew et al. Am. J. Phys. Med. Rehabil. ● Vol. 87, No. 3

the posterosuperior calcaneus. This condition isoften associated with retrocalcaneal bursitis, whichimpinges on the Achilles tendon, thus aggravatingthe problem. Ultrasound features of Achilles tendi-nosis include fusiform swelling or diffuse tendonthickening. There may be focal areas of hypoecho-genicity or more diffuse, homogeneous, low reflec-tivity of the tendon. Figure 10 shows diffuseAchilles tendinosis with characteristic fusiformthickening of the tendon. With insertional tendi-nosis, there may be associated retrocalcaneal bur-sal inflammation and fluid accumulation.

The ultrasound appearance of Achilles tendontears varies according to the timing of the scanafter injury. The gap within the tendon is usuallyfilled with fluid, hemorrhage, and fibrinous debris.However, an organizing hematoma may seem hy-perechoic, making the accurate diagnosis of a full-

thickness Achilles tendon tear difficult.20 In thesecircumstances, dynamic imaging maneuvers dem-onstrating absence of tendon translation across thetear site with squeezing of the calf muscle can beextremely useful in differentiating full-thicknesstears from partial tears. The distal plantaris tendoncourses along the medial aspect of the Achillestendon. In full-thickness Achilles tendon tears, thehyperechoic plantaris tendon may occasionallymimic intact Achilles tendon fibers,18 making itseem as if there is a high-grade partial tear insteadof a complete tear of the Achilles tendon. Dynamicimaging maneuvers, and being aware of the typicalanatomic location of the plantaris tendon, can behelpful in sorting out such dilemmas.

U/S APPEARANCE OF THE LIGAMENTINJURIES OF THE LOWER LIMB

Ligaments share similar ultrasound character-istics to tendons and demonstrate an echogenicparallel fibrillar pattern. These hyperechoic fibersseem more compact than in tendons, and they alsodemonstrate anisotropy.

MEDIAL COLLATERAL LIGAMENTMedial collateral ligament (MCL) injuries of

the knee usually result from a valgus load in apartially flexed knee, or external rotation twist-ing injuries of the knee. The MCL is made up ofsuperficial and deep bands originating from themedial epicondyle of the femur and insertinginto the medial tibia 5–7 cm below the joint line.The deep band is formed by the meniscofemoraland meniscotibial ligaments, which attach to themedial meniscus. The normal MCL on ultra-sound appears as two distinct, broad, parallelhyperechoic bands with hypoechoic loose areolar

FIGURE 7 Patellar tendinosis (jumper’s knee). Longitudinal sonogram demonstrates diffuse thickening ofthe proximal (A) and distal (B) patellar tendon (arrows) with areas of hypoechogenicity (openarrow). C, T2-weighted sagittal magnetic resonance image of patellar tendon, showing degener-ative interstitial tears (open arrows) at the proximal and distal attachments. Pat, patella; tib,tibial tuberosity.

FIGURE 8 Longitudinal sonogram of the patellartendon (arrow) with hyperechoic calcifi-cations (open arrow) and posterior acous-tic shadowing. Pat, patella.

March 2008 Musculoskeletal Diagnostic Ultrasound 243

tissue separating the superficial and deep com-ponents. The deep band often seems slightlymore hypoechoic than the superficial band be-cause of the orientation of the collagen fibers.The injured MCL seems thickened or irregularon ultrasound, with hypoechoic regions of edemaand hemorrhage. A tear of the ligament is seen as

disrupted fibers with intervening hypoechoic he-matoma. Figure 11 shows a partial tear of theMCL, with disruption of the deep band at thelevel of the medial femoral epicondyle.

ANTERIOR TALOFIBULAR LIGAMENTLateral ligament injuries from ankle sprains

are one of the most commonly encountered inju-ries in sports.21 The anterior talofibular ligament(ATFL) is the most commonly sprained ankle liga-ment. The ATFL is located between the fibula andthe talus on the lateral aspect of the ankle, and itresists inversion when the ankle is plantar flexed.Partial tears (grade 1 or 2 injuries) of the ATFL aremore common, and complete tears (grade 3) occurrelatively infrequently.22 The normal ligamentseems hyperechoic, but it may be difficult to isolatebecause of the surrounding hyperechoic fat andcontours of the ankle joint. The anisotropic prop-erties of ligaments can be helpful to identify theligament. Slight changes in the orientation of thetransducer will cause the ligament to become hy-poechoic, whereas the surrounding fat will remainhyperechoic. Realigning the transducer perpendic-ular to the ligament will demonstrate the hypere-choic fibrillar echotexture of the ligament. AnATFL tear appears as a hypoechoic thickening ofthe ligament or disruption of fibers on ultrasound,depending on the grade of tear, as illustrated inFigure 12. Application of the anterior drawer testto the ankle during the scan can accentuate anydefects.23 Other features include outward bowing

FIGURE 10 A, Longitudinal sonogram of Achillestendinosis with fusiform thickening ofthe tendon (arrows) and ill-defined ar-eas of hypoechogenicity. B, Normallongitudinal sonogram of the Achillestendon (arrowhead).

FIGURE 9 Tibialis posterior tendinosis. A, Longitudinal sonogram of the distal tibialis posterior tendon with adegenerative tear (open arrow) just proximal to the accessory navicular (acc). B, Transverse sono-gram showing a markedly thickened tendon with hypoechoic cleft (open arrow) within the substanceof the tendon, consistent with a partial longitudinal tear. A small amount of tenosynovial fluid is seenwithin the tendon sheath (arrows). C, D, Normal longitudinal and transverse sonogram of the distaltibialis posterior tendon (asterisk).

244 Chew et al. Am. J. Phys. Med. Rehabil. ● Vol. 87, No. 3

of the ligament and capsule from hemarthrosis, ora markedly echogenic avulsion fracture of the dis-tal fibula may be present with associated posterioracoustic shadowing.

U/S APPEARANCE OF OTHER JOINTPATHOLOGYAssessment of Joint Swelling

Joint swelling can be caused by simple effu-sions, hemarthrosis, and synovitis. Other periartic-ular fluid-like structures include bursae and cysts.In a simple effusion, the fluid seems hypoechoicand is bounded by the joint capsule. In hemarthro-sis or infection, there may be a diffuse increase inthe echogenicity of the fluid, often with layering offluid or particulate debris. Sometimes, intraartic-ular blood clots may be seen as brightly echogenicmasses. Figure 13 shows a normal, nondistended,suprapatellar recess and a knee-joint effusion withdistension of the suprapatellar recess.

The ultrasound characteristics of simple jointeffusions differ from swelling attributable to syno-vitis. Synovitis may occur in joint capsules, bursae,and tendon sheaths. Synovial proliferation appearsas irregular thickening of the synovium, which hasvariable echogenicity ranging from anechoic to hy-perechoic. There may be diffuse nodular thicken-ing of the joint capsule or bursal margins, or nod-ular thickening of folds of synovium, with anassociated effusion. A normal bursa is not easily

visualized on ultrasound, but it sometimes appearsas a thin hypoechoic cleft or sac. Bursitis is char-acterized by synovial fluid distension manifestingas a hypoechoic structure with well-defined mar-gins, filled with contents of variable echogenicity.Simple bursitis may be characterized by anechoicfluid with or without septations, whereas chronicbursitis often displays moderately echogenic bursalthickening attributable to chronic impingement oroveruse.

The characteristic ultrasound feature of a sim-ple cyst is anechoic fluid collection with posterioracoustic enhancement. Complex cysts, on theother hand, contain internal echoes and septations.Parameniscal cysts may be hypoechoic or anechoic,and they characteristically lie at the margin of theknee joint, usually in direct communication withthe underlying meniscus.24 A coexisting meniscaltear is present in approximately 85% of thesecysts,25 as seen in Figure 14.

A Baker cyst is the most common cyst found inthe posteromedial popliteal fossa. A Baker cyst oc-curs when fluid from the knee joint distends thesemimembranosus bursa lying between the medialgastrocnemius and semimembranosus tendons.26

On ultrasound, a Baker cyst is typically well definedand has a rounded appearance at its cranial andcaudal ends, as seen in Figure 15. A thin neckshould always be demonstrated communicatingwith the deeper subgastrocnemius bursa and the

FIGURE 12 Longitudinal sonogram of (A) normal anterior talofibular ligament (asterisk) and (B) high-gradetear of the anterior talofibular ligament (open arrow). Fib, fibula; tal, talus.

FIGURE 11 Medial collateral ligament (MCL). A, Longitudinal sonogram of the normal MCL. B, Longitudinalsonogram of a partial tear (open arrow) involving the deep band of the proximal MCL. Thesuperficial band remains intact. Fem, femur; tib, tibia; sup, superficial band of the MCL; deep, deepband of the MCL.

March 2008 Musculoskeletal Diagnostic Ultrasound 245

joint space. The cyst may be anechoic or havecontents of varying echogenicity that may includedebris, synovium, hemorrhage, or joint bodies.26 ABaker cyst may rupture, with irregular anechoic orhypoechoic fluid seen tracking beyond the caudalor cranial margin of the Baker cyst, resulting insoft-tissue edema extending down the calf.

Joint BodiesLoose bodies in joints may be the result of an

acute injury producing a detached osteochondralfragment, or chronic conditions such as osteoar-thritis, chronic repetitive trauma, or synovial os-teochondromatosis. The detection of joint bodies isdependent on the demonstration of focal echogenicstructures, which are completely separate fromother structures lying within the joint space andcan be difficult to demonstrate if there is no fluid inthe joint. Joint bodies tend to collect at specificlocations in joints. In the knee, joint bodies arecommonly found in the suprapatellar pouch, lat-eral joint recess, or intercondylar notch. Joint bod-ies can also accumulate within a Baker cyst, wherethey are relatively easy to identify. In the ankle,joint bodies are usually located in the anterior andposterior tibiotalar recesses.

U/S APPEARANCE OF OTHERSOFT-TISSUE PATHOLOGY

Plantar FasciitisInferior heel pain is a common complaint and

is most often attributable to plantar fasciitis.27 Theplantar fascia serves as a common tendon aponeu-rosis for the superficial layer of the intrinsic plan-tar foot muscles. The plantar fascia arises from themedial and lateral inferior calcaneal tubercles toform the medial and lateral bundles. The medialbundle is usually thicker than the lateral and isnormally less than 4 mm thick. The plantar fasciaextends along the plantar aspect of the foot anddiverges to blend with the deep fascia under themetatarsal heads. The plantar fascia serves to main-tain the medial longitudinal arch of the foot, assistsin shock absorption across the foot, and is crucial inallowing the foot to push off in gait.28 Plantar fasciitisis usually attributable to overuse and prolongedweight bearing, and it commonly affects the medialbundle. Factors that contribute to the pathogenesisinclude poor biomechanics, obesity, and certain sys-temic conditions such as seronegative spondyloar-thropathies.29 Plantar calcaneal spurs are frequentlypresent in both symptomatic and asymptomatic indi-

FIGURE 14 A, Longitudinal sonogram across the lateral joint line of the knee depicting a parameniscal cyst(arrow), with an associated tear of the lateral meniscus (open arrow). B, The tear of the lateralmeniscus can be seen in communication with the cyst. Fem, femur; tib, tibia.

FIGURE 13 Longitudinal sonogram of (A) normal suprapatellar recess (arrows) and (B) distended suprapa-tellar recess (open arrow) with a joint effusion. quads, quadriceps tendon; pat, patella; fem,femur.

246 Chew et al. Am. J. Phys. Med. Rehabil. ● Vol. 87, No. 3

viduals, although it is unclear whether these aredirectly involved in the pathogenesis of plantar fasci-itis.29 The U/S features of the plantar fascia are similarto other tendons, which are seen as linear echogenicbands with a fibrillar pattern and very little variationin thickness along its length.30 Plantar fasciitis re-sults in thickening of the fascia to more than 4 mm,with ill-defined regions of hypoechogenicity and,occasionally, peritendinous fluid collections oredema.31 Figure 16 illustrates thickening of theplantar fascia at the attachment to the calcaneus.With continued overuse, the plantar fascia can de-velop partial tears, or it may progress to completerupture.

CONCLUSION

Musculoskeletal imaging is a rapidly evolv-ing field, with continuous improvements in thetechnology and its application. U/S has beenshown to be effective for many applications re-lated to the practice of musculoskeletal medi-cine. As a diagnostic imaging modality, it has theadvantages of being cost-effective and widely

available. Because of its portability, ultrasoundcan allow direct visualization of the anatomicstructures in question within the general contextof the physical examination and clinical evalua-tion of the patient, whereas computed tomogra-phy or magnetic resonance imaging scans areoften not readily available in the clinic. Theability to perform dynamic examinations withreal-time visualization and rapid side-to-sidecomparisons makes U/S eminently suitable andsensitive for the diagnosis of many musculoskel-etal pathologies. Limitations of U/S include itsoperator dependence and long learning curve.Adequate training and supervision may minimizethese limitations; however, training opportuni-ties and certification for musculoskeletal ultra-sound are currently lacking. The paucity ofwidely accepted standard examination protocolsaccentuates the variability of results attributableto operator dependence.32 Despite these limita-tions, U/S, when used appropriately, provides animportant adjunct to physical examination, toaid in the diagnosis of many musculoskeletalpathologies.

FIGURE 15 Baker cyst. A, Longitudinal sonogram demonstrating a well-defined anechoic cystic lesion poste-rior to the femur. A small amount of joint fluid is seen in the posterior knee joint (arrow). B,Transverse sonogram showing the cyst lying between the medial gastrocnemius muscle (G) and thesemimembranosus (SM) tendons. A thin neck of the cyst and an associated channel (open arrow)can be seen communicating with the subgastrocnemius recess. Fem, medial femoral condyle.

FIGURE 16 Longitudinal sonogram of (A) normal plantar fascia (arrows) and (B) plantar fasciitis, demonstrat-ing a thickened hypoechoic plantar fascia (arrows) inserting into the calcaneus (calc).

March 2008 Musculoskeletal Diagnostic Ultrasound 247

REFERENCES1. van Holsbeeck MT, Introcaso JH: Sonography of muscle, in

Bralow L (ed): Musculoskeletal Ultrasound, ed 2. St Louis,Mosby, Inc, 2001, pp 23–75

2. Speer KP, Lohnes J, Garrett WE: Radiographic imaging ofmuscle strain injury. Am J Sports Med 1993;21:89–95

3. Lee JC, Healy J: Sonography of lower limb muscle injury.AJR Am J Roentgenol 2004 February;182:341–51

4. Takebayashi S, Takasawa H, Banzai Y, et al: Sonographicfindings in muscle strain injury: clinical and MR imagingcorrelation. J Ultrasound Med 1995;14:899–905

5. Best TM: Soft-tissue injuries and muscle tears. Clin SportsMed 1997;16:419–34

6. Vanden Bossche L, Vanderstraeten G: Heterotopic ossification: areview. J Rehabil Med 2005;37:129–36

7. Snoecx M, De Muynck M, Van Laere M: Association betweenmuscle trauma and heterotopic ossification in spinal cordinjured patients: reflections on their causal relationship andthe diagnostic value of ultrasonography. Paraplegia 1995;33:464–8

8. Peck RJ, Metreweli C: Early myositis ossificans: a newechographic sign. Clin Radiol 1988;39:586–8

9. Martinoli C, Derchi LE, Pastorino C, Bertolotto M, SilvestriE: Analysis of echotexture of tendons with US. Radiology1993;186:839–43

10. Crass JR, van dV, Harkavy LA: Tendon echogenicity: ex vivostudy. Radiology 1988;167:499–501

11. Khan K, Cook J: The painful nonruptured tendon: clinicalaspects. Clin Sports Med 2003;22:711–25

12. Fomage B, Rifkin M: Ultrasound examination of tendons.Radiol Clin North Am 1998;26:87–107

13. Grobbelaar N, Bouffard JA: Sonography of the knee, a pic-torial review. Semin Ultrasound CT MR 2000;21:231–74

14. Bouffard JA, Dhanju J: Ultrasonography of the knee. SeminMusculoskelet Radiol 1998;2:245–70

15. Frey C, Shereff M, Greenidge N: Vascularity of the posteriortibial tendon. J Bone Joint Surg Am 1990;72:884–8

16. Mosier SM, Lucas DR, Pomeroy G, Manoli A: Pathology ofthe posterior tibial tendon in posterior tibial tendon insuf-ficiency. Foot Ankle Int 1998;19:520–4

17. Niki H, Ching RP, Kiser P, Sangeorzan BJ: The effect ofposterior tibial tendon dysfunction on hindfoot kinematics.Foot Ankle Int 2001;22:292–300

18. Grassi W, Filippucci E, Farina A, Cervini C: Sonographicimaging of tendons. Arthritis Rheum 2000;43:969–76

19. Puddu G, Ippolito E, Postacchini F: A classification of Achil-les tendon disease. Am J Sports Med 1976;4:145–50

20. Jacobson JA: Ultrasound in sports medicine. Radiol ClinNorth Am 2000;40:363–6

21. Osborne MD, Rizzo TD: Prevention and treatment of anklesprain in athletes. Sports Med 2003;33:1145–50

22. Helgason JW, Chandnani W: MR arthrography of the ankle.Radiol Clin North Am 1998;36:729–38

23. Campbell DG, Menz A, Isaacs J: Dynamic ankle ultra-sonography: a new imaging technique for acute ankleligament injuries. Am J Sports Med 1994;22:855–8

24. Chhem RK, Kaplan PA, Dussault RG: Ultrasonography ofthe musculoskeletal system. Radiol Clin North Am 1994;32:275–89

25. Rutten MJCM, Collins JMP, van Kampen A, Jager GJ: Me-niscal cysts: detection with high-resolution sonography.AJR Am J Roentgenol 1998;171:491–6

26. Ward EE, Jacobson JA, Fessell DP, Hayes CW, vanHolsbeeck M: Sonographic detection of Baker’s cysts: com-parison with MR imaging. AJR Am J Roentgenol 2001;176:373–80

27. Cardinal E, Chhem RK, Beauregard CG, et al: Plantarfasciitis: sonographic evaluation. Radiology 1996;201:257–9

28. Schepsis AA, Leach RE, Gorzyca J: Plantar fasciitis: aetiol-ogy, treatment, surgical results and review of the literature.Clin Orthop 1991;266:185–96

29. DeMaio M, Paine R, Mangine RE, et al: Plantar fasciitis.Orthopedics 1993;16:1153–63

30. Wall JR, Harkness MA, Crawford A: Ultrasound diagnosis ofplantar fasciitis. Foot Ankle 1993;14:465–70

31. Gibbon WW, Long G: Ultrasound of the plantar aponeurosis(fascia). Skeletal Radiol 1999;28:21–6

32. Lew HL, Chen CPC, Wang TG, Chew KTL: Introduction tomusculoskeletal diagnostic ultrasound: examination of theupper limb. Am J Phys Med Rehabil 2007;86:310–321

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