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BACKGROUND. Tearing of the superior peroneal retinaculum is a known cause of peroneal tendon subluxation-dislocation. However, with the exception of cortical avulsions at the fibular attachment, superior peroneal retinaculum injury and subsequent peroneal tendon subluxation-dislocation are typically radiographically occult. OBJECTIVE. The purpose of this study was to evaluate the previously undescribed association between radiographic fibular tip periostitis and MRI evidence of peroneal tendon subluxation-dislocation in patients with hindfoot valgus. METHODS. Thirty-five patients with radiographic fibular tip periostitis and 35 ageand sex-matched individuals without periostitis were selected from among 220 consecutively registered patients with hindfoot valgus who had undergone both ankle radiography and MRI. Studies were retrospectively assessed by two musculoskeletal radiologists in consensus and by two additional blinded radiologists independently for the presence of peroneal tendon subluxation-dislocation, presence of subfibular impingement, and hindfoot valgus angle measurements. Interobserver agreement and accuracy, sensitivity, and specificity in the detection of fibular periostitis, peroneal tendon subluxation-dislocation, and subfibular impingement were calculated, and Fischer exact, Mann-Whitney, kappa coefficient, and intraclass correlation tests were performed. RESULTS. Both the consensus and the two independent interpretations showed that the frequency of peroneal tendon subluxation-dislocation was significantly greater in the group with periostitis (62.9%, 65.7%, and 85.7%) than in the group without periostitis (5.7%, 0%, and 14.3%) ( p < .001). The finding of periostitis was specific and highly sensitive for predicting peroneal tendon subluxation-dislocation. The frequency of subfibular impingement was also statistically higher in the group with periostitis than in the group without it ( p < .001). The hindfoot valgus angle was statistically larger in the group with periostitis than in the control group ( p = .01-.002) and among patients with versus those without peroneal tendon subluxation-dislocation ( p = .002 to p < .001). The blinded readers had substantial or almost perfect agreement on all imaging interpretations (concordance rate, 82.9-95.7%; κ = 0.66-0.91). CONCLUSION. The radiographic finding of fibular tip periostitis in patients with hindfoot valgus can be a predictor of peroneal tendon subluxation-dislocation and may also suggest advanced hindfoot valgus and subfibular impingement. These radiographic associations should be recognized by the radiologist, and MRI may be recommended as clinically indicated. CLINICAL IMPACT. Chronic undiagnosed peroneal tendon subluxation-dislocation can be a persistent cause of lateral ankle pain, leading to further degeneration and the possibility of complete peroneal tendon tears. Distal fibular periostitis in patients with hindfoot valgus can be a reliable radiographic indicator of this entity and may suggest the presence of subfibular impingement.

Objective: To evaluate the position of the peroneus longus (PL) tendon relative to the cuboid tuberosity and cuboid tunnel during ankle dorsiflexion and plantarflexion using ultrasound and MRI., Materials and Methods: The study population included two groups: 20 feet of 10 asymptomatic volunteers who underwent prospective dynamic ultrasound and 55 ankles found through retrospective review of routine ankle MRI examinations. The location of the PL tendon at the cuboid tuberosity and cuboid tunnel was designated as completely within the tunnel, indeterminate, or subluxed with respect to ankle dorsiflexion and plantarflexion., Results: On dynamic ultrasound, the PL tendon was perched plantar to the cuboid tuberosity in dorsiflexion, and glided to enter the cuboid tunnel distal to the tuberosity in plantarflexion in all 20 feet. On the MRI evaluation, there was a statistically significant difference (p = 0.0006) in the location of the PL tendon between the ankles scanned in dorsiflexion and plantarflexion., Conclusion: Based on our findings on ultrasound and MRI, the PL tendon can glide in and out of the cuboid tunnel along the cuboid tuberosity depending on ankle position. Thus, "subluxation" of the tendon as it curves to enter the cuboid tunnel, which to the best of our knowledge has not yet been described, should be recognized as a normal, position-dependent phenomenon and not be reported as pathology.

Injuries to the extensor compartment of the ankle are uncommon and often are overlooked or misinterpreted at clinical presentation. Ultrasonography (US) and magnetic resonance (MR) imaging play a critical role in the diagnosis and evaluation of these injuries. US is a dynamic, quick, cost-effective imaging method for assessing ankle extensor compartment injuries as an alternative or adjunct to MR imaging. MR imaging provides multiplanar cross-sectional delineation of regional anatomic structures and also can be used to assess the predisposing cause, estimate the extent of injury, and aid in preoperative planning for requisite surgical repair. The spectrum of pathologic conditions affecting the ankle extensor compartment ranges from tendinosis secondary to degenerative, inflammatory, or depositional disease to traumatic tendon or retinacular rupture and entrapment neuropathy. Major components of the ankle extensor compartment at risk for injury include the anterior tibial, extensor hallucis longus, and extensor digitorum longus tendons; the extensor retinacular mechanism; and the anterior tarsal tunnel. Familiarity with the normal anatomic appearance and pathologic features of the ankle extensor compartment at US and MR imaging as well as potential imaging pitfalls is critical for accurate injury evaluation.

Tendon disorders along the plantar aspect of the foot may lead to significant symptoms but are often clinically misdiagnosed. Familiarity with the normal anatomy of the plantar tendons and its appearance at magnetic resonance (MR) imaging and ultrasonography (US) is essential for recognizing plantar tendon disorders. At MR imaging, the course of the plantar tendons is optimally visualized with dedicated imaging of the midfoot and forefoot. This imaging should include short-axis images obtained perpendicular to the long axis of the metatarsal shafts, which allows true cross-sectional evaluation of the plantar tendons. Normal plantar tendons appear as low-signal-intensity structures with all MR sequences. At US, accurate evaluation of the tendons requires that the ultrasound beam be perpendicular to the tendon. The normal tendon appears as a compact linear band of echogenic tissue that contains a fine, mixed hypoechoic and hyperechoic internal fibrillar pattern. Tendon injuries can be grouped into six major categories: tendinosis, peritendinosis, tenosynovitis, entrapment, rupture, and instability (subluxation or dislocation) and can be well assessed with both MR imaging and US. The radiologist plays an important role in the diagnosis of plantar tendon disorders, and recognizing their imaging appearances at MR imaging and US is essential.

Objective: Posterior tibial tendon dysfunction with secondary hindfoot valgus can lead to painful extraarticular, lateral talocalcaneal, and subfibular impingements, often necessitating surgical intervention. The purpose of this study was to correlate findings of lateral hindfoot impingement with grading of posterior tibial tendon tears and severity of hindfoot valgus on MRI., Materials and Methods: MR images from 75 patients (45 women and 30 men) with MRI evidence of posterior tibial tendon tears were evaluated for grade of posterior tibial tendon tear, hindfoot valgus angle, osseous contact or opposing marrow signal changes at the talus-calcaneus or fibula-calcaneus, peroneal tendon subluxation-dislocation, and presence of lateral malleolar bursa. Statistical analyses were performed using Cochran-Armitage, Fisher's exact, and Mann-Whitney tests., Results: Twenty-eight cases (37%) of lateral hindfoot impingement were identified, including six talocalcaneal, eight subfibular, and 14 talocalcaneal-subfibular impingements. The prevalence of impingement was significantly increased with greater MRI hindfoot valgus angle (p < 0.001). The prevalence of talocalcaneal-subfibular impingement significantly increased with grading of posterior tibial tendon tear (p = 0.018). Peroneal tendon subluxation was present only with advanced hindfoot valgus (p = 0.010) and impingement (p = 0.004). There was no significant association between the presence of lateral malleolar bursa and hindfoot valgus severity., Conclusion: Extraarticular lateral hindfoot impingement is associated with advanced posterior tibial tendon tears and increased MRI hindfoot valgus angle. Peroneal tendon subluxation likely represents an end stage of lateral impingement in patients with posterior tibial tendon dysfunction.

Objective: The MRI features of the proximal rectus femoris musculotendinous junction have scarcely been described in the literature. The purpose of our study, based on a review of 50 asymptomatic and 20 symptomatic MRI studies, was to define the normal MRI anatomy and MRI features of intrasubstance injury of deep musculotendinous tears of the proximal rectus femoris., Conclusion: Axial and coronal MR images are optimal for visualizing the direct and indirect heads, the conjoined tendon, and the deep musculotendinous junction of the proximal rectus femoris. Tears of the deep musculotendinous junction are longitudinal, involving a long segment of the muscle. MRI features include a "bull's-eye" sign, longitudinal scar, retraction, pseudocyst, and hematoma.

The literature describing iliopsoas compartment injuries is based on case reports and small patient series, mostly in the orthopedic literature.Nevertheless, in recent years, there has been a growing recognition of these injuries. Because many intra-articular and extra-articular bony and soft tissue injuries in the groin may clinically mimic each other, because two or more pathologic entities may coexist, and because athletes are highly motivated to continue with their physical activity, diagnosis of iliopsoas injury is often delayed. Thus, cross-sectional imaging is highly important. MR imaging is most accurate for diagnosing nondynamic diseases of the iliopsoas compartment as well as for ruling out other abnormalities of the hip joint and surrounding structures. When a snapping hip is being investigated or corticosteroid injection is warranted, US can be of help in providing a dynamic study and by guiding the injection.

MR imaging is a useful modality for diagnosing and grading proximal rectus femoris injuries.MR imaging is also valuable in predicting the length of recovery and rehabilitation time of musculotendinous strains and in presurgical planning when resection of a chronic hematoma, deep scar tissue, or a pseudocyst is contemplated.

Objective: The aims of this study were to assess, grade, and surgically correlate previously unreported MRI features of superior peroneal retinacular injuries in nine surgically proven cases and to record all soft-tissue and bony abnormalities associated with these injuries., Conclusion: MRI was found to be a useful tool for detecting and grading superior peroneal retinacular injuries and providing information, important for presurgical planning, regarding common concomitant soft-tissue and osseous abnormalities of the lateral collateral ligaments, peroneal tendons, and fibular groove. Superior peroneal retinacular injuries are frequently associated with MRI evidence of peroneal tendon dislocations and tears. Conversely, routine MRI studies may not depict dislocated peroneal tendon injuries, despite clinical history to that effect.

Purpose: To describe the magnetic resonance (MR) appearance and associated clinical findings of partial distal biceps tendon tears., Design: Twenty elbow MR images at 1.5 T, performed over a 7 year period, were reviewed for an appearance of partial tears in the distal biceps. These images were assessed by two musculoskeletal radiologists for the extent of: (a) abnormal signal intensity within the tendon, and the presence of (b) bicipitoradial bursitis, and (c) bony microavulsive injury of the radial tuberosity. Medical records for nine of the 20 cases were reviewed for the clinical findings of ecchymosis, trauma, sensation of a "pop", loss of function, and acuity of onset., Results: Twenty partial distal biceps tendon tears were seen. All displayed an abnormally increased signal in the distal biceps tendon. Three of 20 (15%) showed a 25% to 50% tear, ten of 20 (50%) showed a 50% tear, and seven of 20 (35%) showed a 75% to 90% tear. Bicipitoradial bursitis was seen in 11 of 20 (55%) cases. Bony microavulsive injury of the radial tuberosity was observed in 10 of 20 (50%). Of the nine cases reviewed for associated clinical findings, surprisingly, only three (33%) experienced an acute traumatic episode with an abrupt onset of pain. An insidious onset was reported in four of nine (44%). Sensation of a "pop" was recorded in only two of nine (22%) cases. Ecchymosis and loss of function were not seen in any of the cases. Finally, surgical conformation was obtained for three cases., Conclusion: Partial distal biceps tendon tears have a characteristic MR appearance, demonstrate little functional deficit, and may be attritional in their etiology due to the observation of a low number of patients reporting trauma or an acute onset.

MR imaging, with its unique soft-tissue contrast resolution, noninvasiveness, and multiplanar capabilities, has been applied to the assessment of tendon abnormalities of the foot and the ankle.

Injuries of the peroneal tendons including peritendinosis/tenosynovitis, tendinosis, rupture, dislocation are being detected with greater frequency since the advent of MR imaging. This article focuses on the normal as well as pathologic MR features of the peroneal tendons.

Magnetic resonance (MR) imaging is the imaging modality of choice for evaluation of acute traumatic musculotendinous injuries of the knee. Three discrete categories of acute injuries to the musculotendinous unit can be defined: muscle contusion, myotendinous strain, and tendon avulsion. Among the quadriceps muscles, the rectus femoris is the most susceptible to injury at the myotendinous junction due to its superficial location, predominance of type II fibers, eccentric muscle action, and extension across two joints. Among the muscles of the pes anserinus, the sartorius is the most susceptible to strain injury due to its superficial location and biarticular course. The classic fusiform configuration of the semimembranosus along with a propensity for eccentric actions also make it prone to strain injury. MR imaging findings associated with rupture of the iliotibial tract include discontinuity and edema, which are best noted on coronal images. The same mechanism of injury that tears the arcuate ligament from its fibular insertion can also result in avulsion injury of the biceps femoris. The gastrocnemius muscle is prone to strain injury due to its action across two joints and its superficial location. Injuries of the muscle belly and myotendinous junction of the popliteus are far more common than tendinous injuries.

Purpose: To determine the magnetic resonance (MR) imaging features that characterize tear of the peroneus longus tendon at the midfoot., Materials and Methods: Medical records and MR images in nine patients with a tear of the middle segment of the peroneus longus tendon were retrospectively reviewed. All nine patients had undergone routine ankle MR imaging; three had undergone additional oblique coronal MR imaging. Surgical proof of a tear was available for three patients., Results: Partial tear was present in four patients, and complete tear was present in five. Partial tears were characterized by heterogeneous signal intensity and thickening of the tendon. Complete tears were characterized by discontinuity of the tendon. Additional findings included fluid in the tendon sheath (n = 6), marrow edema of the lateral calcaneal wall (n = 3), enlarged peroneal tubercle (n = 3), and tear of the peroneus brevis tendon (n = 2). The extent of the tear was better assessed with oblique coronal MR images., Conclusion: The characteristic MR imaging appearance of complete or partial tear of the middle portion of the peroneus longus tendon includes foci of increased signal intensity in the distal tendon, morphologic alterations, and/or discontinuity of tendon. Bone marrow edema along the lateral calcaneal wall may be suggestive of the diagnosis. Additional oblique coronal midfoot MR images may help in assessment of the extent of the tear.

Injuries of the peroneal tendons include tendinosis, tenosynovitis, tears, and dislocation. These injuries are being detected with greater frequency since the advent of MRI. After a review of the normal MRI anatomy of the peroneal tendons, this article will focus on the MR features of peroneal tendon disorders in the foot and ankle.

We describe a case of thickening and longitudinal increased signal within the Achilles tendon in a patient denying any recent or previous history of Achilles tendon injury. The MR appearance, while simulating tendinosis or rupture, was compatible with incomplete incorporation of the soleus tendon into the gastrocnemius tendon. This constitutes a normal anatomical variant, not previously described in the radiologic literature, and should not be confused with increased signal and thickening due to disease of the Achilles tendon.

Purpose: The most prevalent, yet unproven, theory for the development of longitudinal splits of the peroneus brevis tendon is the compression of the peroneus brevis tendon by the peroneus longus tendon in dorsiflexion. The goal of our study was to provide insight into this pathomechanism by evaluating the shape of the peroneus brevis tendon and its relationship to the adjacent structures in the fibular groove during plantarflexion and dorsiflexion., Method: The MR images of 13 ankles in asymptomatic adult volunteers were performed in full dorsiflexion and plantarflexion. The axial MR images were assessed for the shape of the peroneus brevis tendon and its relationship to the peroneus longus tendon and posterior cortex of the fibula in both plantarflexion and dorsiflexion., Results: In 12 of the 13 volunteers, the peroneus brevis tendon was located anterior or anteromedial to the peroneus longus tendon in the fibular groove. In those volunteers the peroneus brevis tendon was more flattened and compressed against the fibular groove by the overlying peroneus longus tendon in dorsiflexion than plantarflexion. Fat planes were noted in plantarflexion between the peroneal tendons as well as between the peroneus brevis tendon and the fibular groove. These were obliterated in dorsiflexion., Conclusion: The changes in configuration of the tendon of the peroneus brevis tendon in dorsiflexion compared with plantarflexion provide support to our present understanding of the pathomechanism of longitudinal tears of the peroneus brevis tendon.

Objective: The purpose of this article is to describe the MR imaging appearance of seven cases of posterior tibial tendon dislocation and subluxation., Conclusion: Posterior tibial tendon dislocation is a rare but important entity usually related to a previous traumatic event. The clinical diagnosis is often missed because of its rarity. MR imaging provides important clues to the diagnosis and preoperative evaluation of this condition.

Objective: Our objective is to describe the characteristic MR imaging features of longitudinal tears of the peroneus brevis tendon and to describe pathologic conditions and normal variants that are associated with these tears which may require surgical intervention at the time of primary tendon repair., Materials and Methods: We retrospectively reviewed 10 MR images of asymptomatic volunteers and 31 MR images of 27 patients with evidence of longitudinal splits of the peroneus brevis tendon. Seven of these cases were surgically proven. In addition, we assessed five pathologic conditions and normal variants: lateral collateral ligamentous tears; injuries to the superior peroneal retinaculum; low-lying muscle belly of the peroneus brevis tendon; peroneus quartus muscle; and convex, flat, or irregular retromalleolar groove., Results: In the patient's group, we saw longitudinal splits as clefts and an irregularity of the contour of the peroneus brevis tendon with (71%) and without (29%) signal changes on proton density-weighted and T2-weighted MR imaging sequences. Divisions of the split tendon assumed a characteristic C-shaped configuration that partly enveloped the peroneus longus tendon. Fifteen cases revealed other pathologic conditions and normal variants known to be associated with or to predispose to tears of the peroneus brevis tendon. These include ankle ligamentous tears (n = 3); abnormal superior peroneal retinaculum (n = 4); low-lying muscle belly of the peroneus brevis tendon (n = 1); peroneus quartus muscle (n = 2); and convex, flat, or irregular retromalleolar groove (n = 15). MR imaging revealed tears in all patients with surgical proof (n = 7)., Conclusion: MR imaging is a useful technique for revealing longitudinal tears of the peroneus brevis tendon as well as showing anatomic and pathologic factors associated with or predisposed to tears.

Chronic rupture of the posterior tibial tendon is a common disorder causing a progressive flat foot deformity. MR imaging is an excellent modality for assessing dysfunction of the tendon. It can easily and accurately detect and grade the tears. A variety of secondary soft tissue and bony abnormalities are associated with the tear and can be useful in confirming the diagnosis.

Radiologic assessment of tendon injuries requires familiarity with normal anatomy and the capabilities of available imaging modalities. Tenography, less commonly used nowadays, does not allow direct visualization of tendons, so that partial ruptures and longitudinal splits may go undetected. Ultrasonography can depict tenosynovitis, tendinitis, and complete tendon rupture of the Achilles tendon, but the other tendons are difficult to visualize with this technique. Magnetic resonance (MR) imaging is superior to computed tomography (CT) in the depiction of tenosynovitis and peritendinitis, tendinitis, tendon rupture, and tendon dislocation and subluxation. CT can demonstrate these abnormalities, but accompanying scar tissue or edema, early changes of tendon degeneration, and small amounts of inflammatory fluid are difficult to differentiate with this technique. CT is superior for demonstrating calcifications, convex retromalleolar groove, bone fragments, or spurs that complicate tendon dislocation and rupture. Although the authors prefer MR imaging, they caution that all of the modalities are not always specific and that differentiation between closely related processes such as tendinitis and early tendon rupture is difficult.

Computed tomographic (CT) evaluation of the peroneal tendons was obtained in 25 normal ankles and 30 abnormal ankles studied for trauma. The tendons and associated soft-tissue and bony structures, such as the calcaneofibular ligament, superior and inferior peroneal retinacula, fibular groove, and peroneal tubercle, which have heretofore evaded documentation on routine radiographs, are illustrated and discussed. Special attention is given to normal variations such as convex fibular tip and enlarged peroneal tubercle, which predispose the peroneal tendons to abnormal mechanical stresses. Examples of CT-established peroneal tendon abnormalities in the 30 cases examined are also demonstrated. These abnormalities include subluxation, dislocation, entrapment, and tenosynovitis of the peroneal tendons. The authors believe CT has proved to be an extremely useful and relatively noninvasive imaging tool for the evaluation of peroneal tendon injuries.

Computed tomography (CT) was performed in 42 patients with 49 clinically suspected tears of the posterior tibial tendon. Twenty-eight of the 49 suspected tears were subsequently surgically explored and repaired. Three patterns of tendon abnormalities were recognized on CT scans: type I-intact, hypertrophied, heterogeneous tendon; type II-attenuated tendon; and type III-absence of a portion of a tendon. Types I and II correlated with partial rupture seen during surgery, and type III correlated with complete rupture of the tendon. CT findings were accurate in 96% of the patients who underwent surgery. In four cases (14%), tendon rupture was seen on CT scans, but the extent of the injury was underestimated and the rupture was misclassified. Reactive periostitis of the distal tibia was seen in 71% of diseased tendons and may represent an important factor in the diagnosis of tendon rupture.

Computed tomography (CT) and magnetic resonance (MR) imaging were performed in 32 cases of clinically suspected chronic tears of the posterior tibial tendon. Surgery was performed in 22 patients (69%). Each case was classified radiographically and surgically as normal or a type 1, type 2, or type 3 rupture. The sensitivity and specificity of CT were 90% and 100%, respectively, while those of MR imaging were 95% and 100%. The accuracy in detecting ruptures was 91% for CT and 96% for MR imaging. The overall accuracy, which reflected the percentage of cases correctly diagnosed as well as those correctly classified, was 59% for CT and 73% for MR imaging. Although the differences between the CT and MR imaging parameters were not statistically significant (possibly due to the small population), the results suggest that MR imaging is the method of choice for detecting ruptures of the posterior tibial tendon. MR imaging provided greater definition of tendon outline, vertical splits, synovial fluid, edema, and degenerated tissue. CT was superior to MR imaging in showing associated bone abnormalities such as periostitis, subtalar osteoarthritis, and subtalar dislocation.

Injury to the peroneal tendons is one of the major long-term complications of intraarticular calcaneal fractures and heretofore has been difficult to diagnose by noninvasive radiography. Retrospective review of CT scans of 24 intraarticular calcaneal fractures, obtained shortly after injury, identified 22 cases (92%) of acute peroneal tendon abnormalities. In most of these cases, multiple findings were present. These included lateral displacement in 14 (58%) of 24, impingement by bony fragments in eight (33%), subluxation or dislocation in six (25%), soft-tissue masses around the tendons representing hematomas or early scar tissue in five (21%), and entrapment of the tendons in three (13%). In 10 cases with long-term follow-up, impingement on the tendons by bony fragments correlated well with the subsequent development of peroneal tenosynovitis, while hematoma around the tendons or lateral displacement of the tendons was clinically insignificant. Thus, CT in the immediate postfracture period, can be used to detect and categorize acute peroneal tendon injuries as well as possibly to predict the likelihood and nature of subsequent development of peroneal tenosynovitis.

CT and MRI are both effective in the diagnosis of ankle tendon injuries. MRI is the preferred study, however, because of its superior soft tissue contrast resolution, multiplanar capabilities, lack of beam hardening artifacts, and lack of ionizing radiation. CT can serve as an excellent substitute when financial considerations and availability preclude the use of MRI. CT is also superior in evaluating bony abnormalities associated with tendon injuries.