mri of the foot

10 ■ APPLIED RADIOLOGY© www.appliedradiology.com December 2006

In an article published in the August2006 issue of this journal, the authorsreviewed magnetic resonance imag-

ing (MRI) of the ankle. This article willpresent a review of the use of MRI in theevaluation of the foot, detailing bone andcartilage abnormalities as well as sinustarsi pathology. The discussion willaddress the evaluation of the foot in hind-foot, midfoot, and forefoot subsections.

Foot MRI techniqueDepending on the clinical question,

MRI of the foot should be tailored to a hindfoot, midfoot, or forefoot exami-nation. For hind- and midfoot, a 12- to14-cm field of view is applied. For theforefoot, a 10- to 12-cm field of view isused to image the smaller peripheraljoints in detail.

PositioningSimilar to the ankle, the foot is placed in

a neutral position for high-field-strengthscanners and in approximately 30˚ plan-tar flexion for extremity scanners.

Pulse sequencesThe pulse sequences for the mid-

and forefoot are T1-weighted (T1W) inthe coronal and axial planes, short tauinversion recovery (STIR) in the coro-nal and sagittal or axial planes, and T2-weighted (T2W) in the coronal plane.

For the evaluation of a mass or thediabetic foot, we add T1W sequencesbefore and after intravenous (IV) con-trast (gadolinium chelate) administra-tion. On low-field-strength scanners,these are performed without fat satura-tion; on high-field-strength scanners, fatsaturation is applied. Precontrast fat-suppressed images are essential to avoidthe pitfall of pseudoenhancement of a mass on fat-saturated postcontrastimages when compared with the non–fat-suppressed precontrast images. Thisis because of a narrow dynamic range ofthe contrast display on the fat-saturatedimages when compared with those with-out fat saturation.

Bone and cartilage abnormalitiesTrauma

The talus is a relatively common sitefor osteochondral injury (Figure 1). Themiddle third (in the sagittal plane) of thelateral border and the posterior third ofthe medial border of the talar dome arethe common locations.1 In our anecdotalexperience, the middle third of the

medial talar margin is a more commonsite than the posterior third. The MRIclassification of osteochondral injurieswas presented by Hepple et al2 andstages the talar injuries according to theseverity of the injury and the degree ofthe osteochondral fragment instability.2,3

Fluid between the osteochondral frag-ment and the underlying bone, displace-ment of the fragment, and a fragmentsize >1 cm are signs of an unstableosteochondral fragment. Unstable ornecrotic osteochondral fragments aretreated surgically with drilling and curet-tage. Conservative treatment is preferredwhen the overlying cartilage is intactand the fragment is stable.4

Talar neck fractures can lead toavascular necrosis (AVN) of the proxi-mal fragment. Stress fractures can oc-cur in the talus but are less commonthan calcaneal stress injuries.

Calcaneus stress fractures can have adiffuse or ill-defined geographic mar-row edema pattern (Figure 2). A low-signal fracture line, usually in a verticalorientation, may be visible. Complex

MRI of the foot

Muhammad Ali, MB BS; Tim S. Chen, MD; John V. Crues, III, MD

Dr. Ali and Dr. Chen are Fellows in Mus-culoskeletal Radiology, RadNet Manage-ment, Los Angeles, CA. Dr. Crues is theMedical Director of RadNet Management,and a Volunteer Clinical Professor of Medi-cine, University of California–San DiegoSchool of Medicine, San Diego, CA.

www.appliedradiology.com APPLIED RADIOLOGY©■ 11December 2006

calcaneal fractures secondary to a verti-cal fall mechanism are best evaluatedwith computed tomography (CT).4

CongenitalCoalition of the middle talocalcaneal

joint is second only to calcaneonavicu-

lar coalition. Osseous, fibro-osseous,fibrous, and fibrocartilaginous formshave been described. MRI findings in-clude a direct bony connection or (in thecase of nonosseous coalition) irregular-ity and eburnation of the articulatingsurfaces and visualization of low-signal

fibrous bridging. Medial downslopingof the sustentaculum tali articulatingsurface (Figure 3) instead of the normallateral slope and presence of a dorsaltalar spur (not to be confused with thephysiologic, more proximal dorsal spurat the capsular insertion) are useful

FIGURE 1. A talar dome osteochondral injury. (A) A sagittal T1-weighted image shows a low-signal osteochondral injury in the talar dome. (B) Asagittal short tau inversion recovery image shows high signal in the talar dome, which is compatible with granulation tissue in the osteochondraldefect. (C) A coronal T2-weighted image shows the medial talar dome osteochondral defect.

A B C

A B

B CFIGURE 3. Talocalcaneal coalition.(A) A sagittal T1-weighted imageshows eburnation and irregularity ofthe articulating surfaces (arrow) inthe middle talocalcaneal facet jointin this patient with fibrous coalition.(B) A coronal proton-density fat-saturated image shows that the jointline slopes medially (arrow) insteadof the normal lateral downslope.(C) An oblique coronal proton-density image in another patientshows bony coalition of the middletalocalcaneal facet (arrow). Again,medial downsloping of the jointplane is seen.

FIGURE 2. A calcaneus stress fracture.(A) A T1-weighted image shows ill-defined low signal in the posterior cal-caneus. No discrete fracture line isnoted. (B) A corresponding short tauinversion recovery image clearly re-veals marrow edema associated withtrabecular stress fracture.

MRI OF THE FOOT

A


MRI OF THE FOOT

ancillary findings.5,6 Calcaneonavicularcoalition (Figure 4) is the most commonof the tarsal coalitions.5,6 As with othersites, it can be osseous or nonosseous.An elongated anterior process of thecalcaneus (anteater nose sign) may bepresent.

NeoplasticSome of the more common masses in

the calcaneus include lipomas, solitary

bone cysts, and chondroblastomas. Lipo-mas have characteristic fat signal. Theycan have central calcification or cysticfocus that appears as signal void or fluidsignal, respectively (Figure 5). Bonecysts in calcaneus are more common inthe older age group (>20 years). Theyhave fluid signal and are located in thecalcaneus body more inferiorly as com-pared with the chondroblastomas. Chon-droblastomas are more common in men

in their second or third decade. Theyoccur in a subarticular location and havehigh signal on T2W images and low sig-nal on T1W images because of their car-tilaginous nature. Low-signal foci ofchondroid calcifications and linear low-signal septations may be present.

Miscellaneous pathologyNavicular osteochondrosis (Köhler’s

disease) is seen in younger patients (3 to 7 years of age). Fragmentation and lowsignal on T1W and T2W images are seen.7

It must not be confused with the frag-mented appearance of nonunited ossifica-tion centers. In adults, AVN secondary to trauma can occur (Muller-Weiss dis-ease).8 There is collapse and low signal of the bone on all pulse sequences. Bonychanges seen with subtalar instability and inflammatory arthropathies are dis-cussed with sinus tarsi pathology.

Sinus tarsi pathologyThe sinus tarsi contain 3 ligaments

extending from the talus to the calcaneus.The lateral-most is the continuation of theinferior extensor retinaculum. The cervi-cal ligament has a striated appearance. Itextends from the talar neck to the body ofthe calcaneus in an oblique anteroposte-rior direction, providing stability to thesubtalar joint. The interosseous ligamentis the most medial of the 3. It extendsfrom the talus to the calcaneus in anoblique mediolateral direction (Figure 6).The ligaments limit the inversion of thehindfoot and play an important role inmaintaining the stability of the subtalarjoint. The sinus tarsi is predominantlyfilled with fat and also contains bloodvessels and nerve endings.9,10

A B CFIGURE 4. Calcaneonavicular coali-tion. (A) A sagittal T1-weighted imageshows irregularity and eburnation ofthe articulating surfaces in this patientwith fibrous coalition of the calcaneo-navicular joint (arrow). (B) An axialshort tau inversion recovery imageshows marrow edema (arrow) in thenavicular adjacent to the fibrouscoalition. (C) An axial proton-densityimage in another patient shows bonycoalition (arrow) between the anteriorprocess of the calcaneus and thenavicular.

A B

FIGURE 5. Calcaneal lipoma. (A) An axial T1-weighted image shows a large fat-signal mass inthe calcaneus (lipoma), with central low-signal fluid secondary to cystic change. (B) The fattycomponent of the lipoma is not discernable on this axial short tau inversion recovery imagebecause of fat nulling. Only the central fluid component is seen.


The ligaments can be torn secondaryto acute trauma or more commonly bychronic recurrent microtrauma. Thiscan lead to subtalar instability withresulting degenerative changes in thejoint. Articular surface irregularity and

subchondral sclerosis with or withoutsubchondral edema can be seen. Poste-rior talocalcaneal facet is involved to agreater degree. Normal fat signal in thesinus tarsi is replaced with edema orfluid signal. There is associated nonvi-

sualization of the torn sinus tarsi liga-ments (Figure 7).

Ankle, subtalar, and tarsal joints canbe affected by inflammatory arthrop-athies (Figure 7), such as Reiter’s dis-ease, or crystal deposition disease, such

FIGURE 6. Anatomy of sinustarsi ligaments. (A) This sagit-tal T1-weighted image (T1WI)shows the cervical ligament(arrow) extending from thetalar neck to the calcaneus. (B) A coronal T1WI of the inter-osseous ligament (encircled) inthe sinus tarsi. Note the normalfat in the sinus tarsi. (C) Aninterosseous ligament (arrow)is seen on this more medialsagittal T1WI.

A B

C

FIGURE 7. A patient with symptoms of sinus tarsisyndrome. (A) This sagittal T1-weighted imageshows low-to-intermediate signal tissue replacingthe normal fat in the sinus tarsi. The ligamentsare not seen. (B) A coronal T2-weighted imageshows edema in the sinus tarsi (arrow). Normalligaments are not visible. This is compatible witha tear of the sinus tarsi ligaments. (C) Anotherpatient with sinus tarsi edema. In this case, theshort tau inversion recovery coronal imageshows erosive changes in the talus and calca-neus in addition to edema. This patient hasrheumatoid arthritis.

A

B

FIGURE 8. Plantar fascitis. (A) A sagittal T1-weighted image shows thickening and indis-tinctness of the plantar fascia. (B) The moresensitive sagittal short tau inversion recoveryimage shows the same, with better depictionof the mild associated edema in the adjacenttissues (arrow).

A B C

MRI OF THE FOOT


MRI OF THE FOOT

as gout. MRI can reveal inflamed syno-vium in addition to the bony erosions andedema. Masses, such as ganglion cystsand lipomas, can occur and lead to painfrom compression of nerve endings.9,10

Hindfoot pathologyPlantar fasciitis is most pronounced

within 2 to 3 cm of the calcaneal attach-ment. It manifests as a smooth thicken-ing (>4 mm) of the plantar fascia, with

adjacent subcutaneous edema. Edemamay also be seen in the calcaneus at the insertion site of the plantar fascia(Figure 8). It is associated with a plantar calcaneal spur in approximately 50% of cases.

Tears of the plantar fascia occur mostcommonly in the midportion of the fas-cia. This is more distal to the typical loca-tion of plantar fasciitis (Figure 9). Theycan be partial or complete. Trauma is theusual etiology. Discontinuity and wavi-ness of the fascial cords with adjacentsoft tissue edema are seen on the MRI.11

Plantar fibromatosis is nodularfibrous proliferation of the plantar fas-cia. The appearance can vary from awell-circumscribed low-signal lesion onall pulse sequences to a locally invasivelesion with ill-defined borders and inter-mediate signal (Figure 10). This is a dif-ficult lesion to treat because of itstendency to recur following local resec-tion.11-13 Differential diagnoses include

FIGURE 9. Plantar fascia partialtear. (A) A sagittal short tau inver-sion recovery image shows partialdiscontinuity in the plantar fasciafibers (arrow) and waviness of thetorn fibers. The plantar fascia isalso thickened. (B) A coronal T2-weighted image reveals that themedial cord of the plantar fascia isdiffusely thick. There is focal fluidreplacing the torn fibers of the fas-cia (arrow).

A B

FIGURE 10. Plantar fibroma. (A) A coronal T1-weighted image shows a large low-signal mass that involves the medial cord of the plantar fascia(arrows). (B) The mass is persistently low to intermediate in signal on this coronal T2-weighted image, which is typical for a plantar fibroma. (C) Inthis sagittal short tau inversion recovery image, the mass shows intermediate signal.

A B C

A B C

FIGURE 11. Lisfranc ligament tear. (A) On this axial T2-weighted image, normal signal and ori-entation of the Lisfranc ligament (arrow) can be seen. (B) An axial T1-weighted image in a patientwith a Lisfranc ligament tear shows an absence of the normal low-signal band (arrow). (C) Anaxial short tau inversion recovery image at the same level as (B) shows marrow edema in thebase of the second metatarsal and the anterolateral corner of the medial cuneiform. Fluid is replacingthe torn Lisfranc ligament (arrow).


soft tissue masses (such as giant celltumor) and sarcomatous neoplasm (suchas synovial sarcoma and fibrosarcoma).A well-circumscribed appearance andhomogenous low-signal characteristicssuggest fibromatosis.14-16

Osseous abnormalities of the hind-foot were discussed earlier.

Midfoot pathologyTrauma

A traumatic tear of the Lisfranc liga-ment (a short bandlike ligament thatextends from the plantar anterolateral

corner of the medial cuneiform to theplantar posteromedial corner of thebase of the second metatarsal) is animportant injury (Figure 11).17 It canlead to instability and progressive dis-organization of the Lisfranc joint.Additionally, there can be loss of themedial longitudinal arch. The ruptureof the ligament fibers is more commonthan is the avulsion fracture at the bonyattachments.17-19 It is an important diag-nosis, since early internal fixation maygive the ligament a chance to heal andcan help to avoid the need for future

arthrodesis. Even with early interven-tion, the success rate is <50%.

The tarsal bones are a common site of trabecular stress injury. Marrow ed-ema with a lack of a clear fracture line ispresent.

The flexor hallucis longus (FHL)tendon is prone to tendinosis and tearsat the knot of Henry. The mechanism is chronic repetitive friction with theflexor digitorum longus (FDL) tendonfrom activities like jogging.20 This is analogous to the intersection syndromebetween the first and second extensor

MRI OF THE FOOT

A B

FIGURE 12. Synovial sarcoma. (A) A sagittal T1-weighted image shows a lobulated low-to-intermediate signal mass (arrows) that involves the tarsalbones and the base of the metatarsal (arrowhead). (B) A sagittal T2-weighted image shows high signal in the same mass (arrows). Smooth, lobulatedmargins underrepresent the aggressive nature of this neoplasm and can sometimes be misleading.

FIGURE 13. Neuropathic changes. (A) A sagittal T1-weighted image shows disorganization of the talonavicular joint with fragmentation, sub-chondral eburnation, and synovial thickening. There is mild inferior “sagging” of the talar head (arrow). Irregularity of the talar dome is alsonoted. (B) A sagittal short tau inversion recovery image shows a subchondral cyst in the navicular. The marrow edema in this case is centeredon the joint, which supports the diagnosis of neuropathic joint over osteomyelitis in this diabetic patient.

A B


compartment tendons in the wrist. Themedial plantar nerve branches can getentrapped between the knot of Henry andthe abductor hallucis muscle, leading tofirst and second toe plantar dysesthesias.

NeoplasticSynovial sarcoma is a malignant neo-

plasm with predilection for the foot. It ispredominantly seen in patients betweenthe ages of 15 and 40 years. It is an ag-gressive neoplasm with a posttreatment 5-year survival rate of approximately55%.21,22 Local recurrence and pulmonaryand bone metastasis are common. OnMRI, it appears as a well-defined masswith a heterogeneous low signal on T1Wimages. On T2W images, it has a hetero-geneous high signal (Figure 12). Cysticareas are common. Fluid-fluid levels canbe present in close to 20% of cases. Fociof calcifications can lead to areas of lowsignal on T2W images. Heterogeneousenhancement is seen with IV contrast ad-ministration. It usually displaces the adja-cent structures rather than invading them.Sometimes a small size, slow growth, andwell-circumscribed appearance can leadto an erroneous diagnosis of a benignmass.23 Other soft tissue neoplasm, benignand malignant primary bony neoplasm,and, less commonly, metastasis can allinvolve the midfoot.

ArthropathyThe Lisfranc and Chopart (intertarsal)

joints are commonly disrupted in neuro-pathic arthropathy (Charcot joint). Rapiddestruction of the joints and bones is therule if protective measures are not takenearly in the process. Therefore, earlydetection of neuropathic changes is veryimportant. Signs on MRI include tear ofthe Lisfranc ligament and edema in thetarsal and metatarsal bones adjacent tothe joints. Loss of normal bony relation-ship and articular and osseous destructionare advanced findings (Figure 13).24-26

A common clinical question is the dif-ferentiation between osteomyelitis and aneuropathic joint. Certain findings (suchas the presence of more focal involvementof the bones, skin ulcers, sinus tracts, andabscess) are more suggestive of infection

MRI OF THE FOOT

A

B

C

FIGURE 14. Osteomyelitis. (A) A coronal shorttau inversion recovery (STIR) image shows focalfluid signal in the deep soft tissues of this diabeticpatient (small arrow). This finding could be asmall abscess or just inflammatory tissue. A skinulcer is barely visible (big arrow). (B) A contrast-enhanced coronal T1-weighted image (T1WI)shows enhancement in the inflammatory tissue.A small nonenhancing area is consistent with anabscess (small arrow). The ulcer (big arrow) isalso better visualized. This shows the value ofintravenous contrast administration in the evalu-ation of a diabetic foot. (C) An axial STIR imagein the same patient shows high signal in themetatarsal (arrow). The corresponding T1WI(not shown) exhibited low signal. These findingsare consistent with osteomyelitis.

A

B

C

FIGURE 15. Anatomy of the plantar capsu-loligamentous complex of the metatarsopha-langeal joint. (A) A sagittal short tau inversionrecovery (STIR) image shows the plantarplate (arrow) attachment to the base of theproximal phalanx. (B) A sagittal STIR image ina plane more lateral to the plantar platereveals the hallux sesamoid (arrows) in theflexor hallucis brevis tendon. (C) An axial T1-weighted image shows the two hallux sesa-moids (arrows) with a normal marrow signal.


(Figure 14). In early neuropathic joint, the signal abnormalities are centered on the joint. However, a clear distinction be-tween infection and neuropathic changesis not always possible with imaging.

The midfoot is often involved inarthropathies such as gout and rheuma-toid arthritis. The findings on MRI in-clude erosions, bone marrow edema,and synovitis. In the absence of a correl-ative history, these can be confused withosteomyelitis. Degenerative changes in the midfoot can be seen with alteredmechanics or can be posttraumatic.

Forefoot pathologyTrauma

“Turf toe” refers to a capsuloligamen-tous injury of the metatarsophalangeal(MTP) joint of the first toe. The mecha-nism of injury includes anterior thrust ofthe metatarsal head in a hyperextendedjoint with a relatively fixed great toe. Thisis common in sports played on syntheticturf, like football, hence the name turftoe. There is stretching and tearing of theplantar capsule and tearing of the plantarplate. The plantar plate is a fibrocartilagi-nous structure that extends from themetatarsal neck to the base of the proxi-mal phalanx. It reinforces the plantar capsule and also attaches the halluxsesamoid bones to the base of the proxi-mal phalanx (Figure 15). Discontinuityof the plantar plate and focal edema andfluid is seen. Associated proximal dis-placement of the hallux sesamoids maybe seen.27,28

Collateral ligament tears are also morecommon in the great toe. Varus or valgusforce is the usual etiology. Edema anddiscontinuity of the medial or lateral col-lateral ligaments is present (Figure 16).The MTP collateral ligament tear ismore common than that of the interpha-langeal joints.29

Hallux sesamoids can be involved withfractures, AVN, and sesamoiditis sec-ondary to inflammatory arthropathies orosteomyelitis. The medial sesamoid ismore commonly involved with trauma,and lateral sesamoid tends to get AVN.Replacement of the normal marrow fatsignal with edema signal can be seen.

MRI OF THE FOOT

A B

FIGURE 16. A metatarsophalangeal (MTP) collateral ligament injury. (A) An axial T1-weightedimage of the first MTP joint shows an indistinct and intermediate-signal medial collateral liga-ment (long arrow). Compare this with the normal low-signal lateral collateral ligament (smallarrow). (B) An axial short tau inversion recovery image shows a grade 2 sprain of the medialcollateral ligament (arrow).

A B

FIGURE 17. Freiberg’s infraction. (A) An axial T1-weighted image shows deformity and col-lapse of the second and third metatarsal heads (arrows). Repetitive microtrauma is the pro-posed underlying etiology. (B) Axial short tau inversion recovery images show the marrowedema from trabecular bone injury in the second metatarsal head and the associated collapseof the second and third metatarsal heads (arrows).

A B

FIGURE 18. Pressure lesion. (A) A sagittal T1-weighted image shows a low-signal ill-definedsoft tissue signal just below the metatarsophalangeal joint (arrow). It has a flat appearanceand does not have a masslike morphology. (B) A coronal T2-weighted image shows the samelesion with intermediate signal and without a masslike contour. The location and MR charac-teristics in this diabetic patient are consistent with a pressure lesion.


Freiberg’s infraction of the metatarsalheads is characterized by fissuring, osteo-necrosis, and eventual collapse of thesubchondral bone (Figure 17). The sec-ond and third metatarsal heads are mostcommonly affected.27 Repetitive micro-trauma and vascular compromise are the

most popular theories of the etiology. It ismore common in young women and maybe secondary to the wearing of high heels.In its acute stage, there is a marrowedema pattern. In its chronic phase, thereis deformity of the metatarsal head andassociated degenerative arthritis.

“March fracture” is a stress fracture ofthe metatarsal neck.27 The name comesfrom its common occurrence in militaryrecruits. It is predominantly seen withactivities that place excessive stress on themetatarsals, such as ballet dancing andgymnastics. Marrow edema and adjacentsoft tissue edema are seen in early stages.Periosteal thickening is present in the subacute stage as a healing response.

NeoplasticPressure lesions are fibrofatty lesions

that occur in the subcutaneous fat. Thesetypically develop at the load-bearingbony prominences, including the plantaraspects of the first and fifth metatarsalheads or below the calcaneal tuberosity.These lesions are of low signal on T1Wimages and of variable signal (intermedi-ate-to-high signal) on T2W images. Theycan have fat in the interstices. Sometimesthey can develop central cystic changes.They generally lack the well-definedmorphology of a mass, and their appear-ance is that of an ill-defined fibrotic tissue (Figure 18). The characteristiclocation and interspersed fat in the lesionfavor the diagnosis and help differentiateit from a neoplasm.24

Morton neuroma is a focal perineuralfibrosis of the plantar interdigital nerves.It is not a true neuroma. The most com-mon location is the third and fourth web

MRI OF THE FOOT

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FIGURE 19. Morton neuroma. (A) A coronal T1-weighted image (T1WI) without fat saturation(low-field scanner) shows an intermediate-signal-intensity mass (arrows) in the plantar aspectof the second web space. (B) A coronal T1WI without fat saturation after the administration ofintravenous contrast shows diffuse enhancement in the Morton neuroma (arrows). On high-field scanners, fat saturation is desirable because it increases the conspicuity of the mass.

A

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FIGURE 20. A giant cell tumor of the tendonsheath. (A) A coronal T1-weighted imageshows a low-signal mass (arrow). The mass isinseparable from the flexor tendons. (B) On acoronal short tau inversion recovery image, themass is persistently low in signal (arrow)—a finding that is consistent with a giant celltumor of the tendon sheath.

FIGURE 21. Gout. (A) An axial T1-weighted image shows a low-signal gouty tophus eroding theadjacent bone (arrow) to form the typical punched-out erosion with an overhanging edge. (B) Anaxial short tau inversion recovery (STIR) image at a slightly different slice position shows thebone erosions. The signal of the gouty tophus tissue is heterogeneously intermediate on STIR.The signal of the tophi on fluid-weighted sequences is typically low to intermediate.

A B

spaces between the plantar aspects of themetatarsal heads.30-32 It is more commonin women, and, once again, the wearingof high heels is implicated as a causativefactor. Other etiologic possibilities in-clude the compression of the nerves bythe intermetatarsal ligament or a dis-tended intermetatarsal bursa. Pain in theweb space with or without radiation tothe toes is the usual presenting symptom.These are small lesions that are nearlyisointense to the muscles on T1Wimages, are intermediate to high in signalon T2W images, and can be isointense to fat (Figure 19). Fat-suppressed IVcontrast-enhanced T1W images give thehighest lesion conspicuity because ofintense lesion enhancement. It can be amobile lesion and can change positionsin the intermetatarsal space.32

A giant cell tumor of the tendon sheathis a relatively common benign lesion. It isa focal form of extra-articular pigmentedvillonodular synovitis. It is low in signalon T1W images and is low-to-intermedi-ate signal on T2W images (Figure 20).

Other masses, such as foreign bodygranulomas, ganglion cysts, and malig-nant neoplasms (like synovial sarcomasor metastasis) can all occur in the fore-foot location.

ArthropathyThe MTP joint of the great toe is the

characteristic location for gout. Monoar-ticular involvement is common but notthe rule. Gouty tophi cause characteristicerosions with punched-out, overhangingedges of the periarticular bones. Theyalso occur at extra-articular locationswith associated osseous erosions. Tophihave low signal intensity on T1W imagesand low-to-intermediate signal intensityon T2W images (Figure 21).33 Variableenhancement is seen with IV contrastadministration. Septic arthritis shouldalways be considered in the differentialdiagnosis of monoarthritis. Rheumatoidarthritis and Reiter’s disease are othercommon arthropathies in the forefoot.Osteoarthritis commonly involves thefirst MTP joint as well.

ConclusionMRI is the imaging modality of choice

for evaluation of musculoskeletal pathol-ogy, including the soft tissue and osseoustrauma, neoplasms, and inflammatorypathology. Compared with CT, MR pro-vides a superior contrast resolution andexquisite detail of soft tissue structures. Italso surpasses CT in the evaluation of tra-becular bone injury. The strengths of MRIin evaluating various foot pathologieshave been briefly reviewed in this article.

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MRI OF THE FOOT

mri of the foot

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