eMedicine Specialties > Radiology > Musculoskeletal

Ankle, Tibialis Posterior Tendon Injuries

Sherif Wassef, MD, MS, FRCS, Consulting Staff, Department of Vascular and Interventional Radiology, Hahnemann University Hospital
Maha Mikhail, MD, MS, FACC, Consulting Staff, Connecticut Multispecialty Group

Updated: Feb 5, 2008

Introduction

Background

Ankle, tibialis posterior tendon injuries. Axial T2-weighted fat-suppressed MRI in an adult man with peritendinous edema. Image reveals reactive marrow edema (open arrow) under the tibialis posterior tendon groove; this is caused by tibialis posterior tendon dysfunction.

Ankle, tibialis posterior tendon injuries. Lateral tenogram shows extrinsic compression on tibialis posterior tenograms at the level of the tibial plafond produced by the flexor retinaculum (between arrowheads). This should not to be mistaken for pathologic adhesion or stenosis. Note the injecting needle (arrow).

Ankle, tibialis posterior tendon injuries. Same patient as in Image 39 in Multimedia; transverse sonogram in a middle-aged woman with tendinosis shows an enlarged inhomogeneous tibialis posterior tendon (between calipers).

Related eMedicine topics:

Ankle, Flexor Hallucis Longus Tendon Injuries

Acquired Flatfoot

Achilles Tendon Pathology

Achilles Tendon Injuries and Tendonitis

Achilles Tendon Rupture

Achilles Tendonitis

Pathophysiology

Risk factors

Tibialis posterior tendon dysfunction is encountered as a result of altered mechanics of the foot or as a response to systemic articular disease. Systemic risk factors are noted more frequently in dysfunction of the tibialis posterior tendon than in disorders of the Achilles tendon. These risk factors include hypertension; obesity; lupus; gout; rheumatoid arthritis; and, less commonly, Reiter syndrome. Patients with rheumatoid arthritis more frequently develop synovitis than tears. This synovitis causes fibrosis from recurrent inflammatory episodes and, eventually, tibialis posterior tendon dysfunction.^7,8,9,10

Young athletes involved in tennis, soccer, ice hockey, basketball, and ballet dancing are vulnerable to traumatic injury to the tendon. Prior trauma and surgery are not strong predictors of tibialis posterior tendon disorder, nor is systemic steroid exposure. However, the direct injection of steroids into the tendon can cause tibialis posterior tendon tears. Unilateral involvement occurs in approximately 90% of cases, with a left-sided predominance.

Human leukocyte antigen Cw6 is a marker of a subtype of seronegative arthropathies, and a positive result with a Cw6 test is associated with tears of the tibialis posterior tendon.

Classification and stages

Jahss has classified disorders of the tendons around the ankle and in the foot according to the following general categories: tenosynovitis, tears, tethering, dislocations, tumors and pseudotumors, ossification, congenital anomalies, contractures, and iatrogenic injuries.^11,12

Clinically, the initial presenting stage of tibialis posterior tendon tenosynovitis is paratendinitis (or preferably peritendinosis) or synovitis (see Image 1). The next stage is tendinitis, which is correctly termed tendinosis. Tendinitis is the less-preferred nomenclature because the pathophysiology is degenerative dysfunction without a true inflammatory component. True tendinitis of the tibialis posterior tendon is unusual (see Image 2).

Many cases that are clinically believed to be tendinitis are in fact synovitis. In tendinosis, patients have degeneration in the tibialis posterior tendon. This is usually associated with paratendinosis/synovitis (see Images 3-4). Histologically, no inflammation is present, but there is evidence of intratendinous collagen degeneration, local necrosis, calcification, and hypocellularity similar to that seen in Achilles tendon degeneration.

By definition, a tethered tendon is one with a limited range of movement, owing to its abnormal fixation to an adjacent structure. Causes of such tethering include anatomic anomalies, such as a single tendon sheath surrounding 2 tendons that normally have separate sheaths or an accessory tendon that increases the volume of tissue within a single sheath; fractures with resulting deformities that lead to abnormal fixation or displacement of the tendon or its sheath; and fracture-dislocations of the ankle that may lead to tethering or even incarceration of 1 or more regional tendons.

The transition stage of tibialis posterior tendon disorder involves microscopic and eventually macroscopic tears of the tendon fibers. Partial tears can scar over and lead to tendon thickening; they can retract and lead to tendon thinning; or they can severely weaken the tendon and result in a gap.

Thin tendons are atrophic (see Images 5-6), and thick tendons are hypertrophic (see Image 7). Most patients have mixed regions of hypertrophic and atrophic tendons. This mixture occurs because of interstitial tendon tears with bulbous hypertrophic proximal tendon fibers and because of retraction of the distal atrophic fibers (see Image 8).

Partial or complete tears of the tendons of the foot and ankle may be related to laceration, especially in the sole of the foot; more commonly, they occur spontaneously. Spontaneous rupture of these tendons usually implies some type of intrinsic pathologic process because normal tendons rarely rupture in this fashion. In older persons or in younger persons (particularly athletes) with chronic inflammation, tendon degeneration may predispose them to spontaneous rupture. However, this is classically seen in persons aged 40-60 years (average age, 55 y), and two thirds of cases occur in women. A tibialis posterior tendon tear with a gap is unusual. The tibialis posterior tendon and the Achilles tendon are most frequently affected.

A similar continuum of tibialis posterior tendon disorders occurs in the Achilles tendon, and a similar concept of cumulative injury is useful in understanding tibialis posterior tendon disorders. However, in distinction to injuries of the Achilles tendon, complete tears with a gap that shows no evidence of fibrosis are fairly unusual manifestations of tibialis posterior tendon dysfunction, and ischemia appears to be a more important causal factor.

Normally, a small amount of fluid is present around the tendon (see Image 9). If too much fluid is present, the patient may have pain and dysfunction. Also, fibrotic synovium contributes to the pathophysiologic process, causing a thickened tendon. Additionally, fibrosing tenosynovitis, related to paratendinitis and synovitis, causes thickening of the tendon. In fibrosing tenosynovitis, the synovium may appear black on MRIs. The dark, adherent synovium makes the tendon appear hypertrophic.

The typical location of tibialis posterior tendon disorders is perimalleolar, although they are centered somewhat distal to the malleolus. A second location at which disorders occur is distal. Distal locations are typical for injuries in young athletes and in patients with inflammatory arthropathies.

Dislocation of the tibialis posterior tendon is a rare injury that is often diagnosed late. The tibialis posterior tendon can also sublux outside its groove, often subtly.

Frequency

United States

The tibialis posterior is, by far, the most frequently ruptured tendon in the rear foot, but injuries to this structure are often overlooked.

Bilateral abnormalities of the tibialis posterior tendon are more common in cases associated with underlying disease, particularly rheumatoid arthritis (see Risk factors, under  Pathophysiology, for other systemic risk factors). Unilateral involvement occurs in approximately 90% of cases, with a left-sided predominance.

Mortality/Morbidity

No data directly link tibialis posterior tendon dysfunction with mortality. However, many comorbid states probably predispose individuals to this condition. Examples include hypertension; obesity; lupus; gout; rheumatoid arthritis; and, less commonly, Reiter syndrome.

Race

No data suggest that any particular race is more vulnerable to tibialis posterior tendon dysfunction.

Sex

Tibialis posterior tendon dysfunction is a disorder that primarily occurs in women who are middle-aged or elderly. Classically, two thirds of spontaneous ruptures occur in women in their fifth or sixth decade of life.

Age

This disorder is bimodal, manifesting in young athletes and, to a greater extent, in middle-aged and elderly women. Classically, two thirds of spontaneous ruptures occur in women in their fifth or sixth decade of life.¹³

Anatomy

Ankle, tibialis posterior tendon injuries. Drawing shows the relationship of the tibialis posterior tendon to the remainder of the tarsal tunnel. Note the relative sites and the distal extent of tendon sheaths in black. Also note that the flexor hallucis and flexor digitorum tendons cross distally at the knot of Henry (straight arrow). Last, note the tibial artery and nerve (curved arrow) between the flexor digitorum longus tendon and the flexor hallucis longus tendon in the tarsal tunnel. ATT, anterior tibialis tendon; FDL, flexor digitorum longus tendon; FHL, flexor hallucis longus tendon; FR, flexor retinaculum; and PTT, tibialis posterior tendon.

Ankle, tibialis posterior tendon injuries. Drawing shows the complex insertions of the tibialis posterior tendon beneath the undersurface of the foot with the muscle dissected away. Note the main slip inserting onto the tubercle of the navicular. Also note the close anatomic relationship of the distal tendon, spring ligament, and distal deltoid ligament. C, calcaneus; N, navicular; PTT, tibialis posterior tendon.

Numerous tendons extend from the lower portion of the leg across the ankle and into the foot. With the exception of the Achilles tendon, all of these tendons change from a vertical orientation in the lower leg to a horizontal orientation near the level of the ankle or in the foot (see Image 10). This modification in direction is accomplished by means of a pulley system consisting of either bone (eg, malleoli) or retinacula to promote their smooth, angular movement about the ankle, subtending a smooth curvy course, in contradistinction to disease process when this is lost (see Image 11).^{14,15,16,17,18}

The tibialis posterior muscle originates from the interosseous membrane and the adjacent posterior surface of the tibia in the proximal third of the leg. The tendon forms in the distal third of the leg and lies closely apposed to the tibia in the posteromedial aspect. Distally, the tibialis posterior tendon sits in a medial or posterior concavity on the medial edge of the posterior tibia. Just lateral to the tibialis posterior tendon lies the flexor digitorum tendon. The tibialis posterior tendon curves distally around the medial malleolus. At this level, the position of the tendon beneath the flexor retinaculum (laciniate) prevents the flexor tendons from bowstringing as they curve around the malleolus. The flexor retinaculum is the roof of the tarsal tunnel. The tarsal tunnel contains the 3 ankle flexor tendons, the adjacent posterior tibial artery and vein, and the tibial nerve (see Image 10).¹⁹

The tibialis posterior tendon next passes under the flexor retinaculum and over the deltoid ligament into the foot and, then, beneath the plantar calcaneonavicular ligament. The tendon contains a sesamoid fibrocartilage, as it runs under the plantar calcaneonavicular ligament. It is inserted into the tuberosity of the navicular bone and gives off fibrous expansions: one expansion passes backward to the sustentaculum tali of the calcaneus, and others pass forward and lateralward to the 3 cuneiforms, the cuboid, and the bases of the second, third, and fourth metatarsal bones (see Image 12).

Because an abnormal size may be the only indicator of tendon dysfunction, the relative sizes of the tibialis posterior tendon, the flexor digitorum tendon, and the flexor hallucis tendon should be examined. In a healthy person, the tibialis posterior tendon is roughly twice the size of the 2 adjacent tendons (see Images 13-15). Additionally, the tibialis posterior tendon should be slightly smaller than the tibialis anterior tendon, and the tibialis posterior tendon should be slightly smaller than the summated measurements of the peroneus brevis and peroneus longus tendons (see Images 13-14).

Blood supply

The proximal aspect of the tibialis posterior tendon is supplied by branches of the posterior tibial artery. The distal aspect of the tendon, at the enthesis, is supplied by the posterior tibial and dorsalis pedis arteries. The midtendon, similar to the Achilles tendon, is poorly supplied with blood. In addition, the mesotendon is absent distally because the synovial sheath ends at the mid portion of the talus. Because of the zone of hypovascularity and because of the absence of a mesotendon, the level of the medial malleolus in relation to the tubercle is the most common location for tibialis posterior tendon dysfunction.

Tibialis posterior tendon disorders are predominantly ischemic, and similar to myocardial infarction, they are senescent diseases. Impingement also plays a role in tibialis posterior tendon dysfunction because the tibialis posterior tendon has a focal point of stress as it curves around the medial malleolus. This point of stress can be analogous to the pressure on the rotator cuff in the subacromial space. This combination of ischemia and mechanical compression causes most tibialis posterior tendon disorders.

Functional anatomy

The tibialis posterior muscle plantarflexes the ankle and inverts the foot. During normal gait, this muscle unit creates a rigid midfoot lever for forward propulsion by locking the calcaneus to the cuboid and the talus to the navicular. If tibialis posterior dysfunction is present, the lack of a rigid midfoot causes gastrocnemius and soleus flexion to occur at the midfoot instead of at the metatarsal heads. This problem eventually leads to midfoot collapse, forefoot abduction, and heel valgus. These deformities are exacerbated by the action of the peroneus brevis, the antagonist muscle to the tibialis posterior. Because the cross-sectional area of the peroneus brevis is half that of the tibialis posterior tendon, a significant degree and length of time of tibialis posterior dysfunction must be present before these abnormalities appear.

Normally, a small amount of fluid is present around the tendon (see Image 9).

Presentation

Early diagnosis and treatment may prevent considerable disability and surgery.

The presenting signs and symptoms are pain, difficulty walking, and swelling along the medial malleolus and the arch of the foot. These signs and symptoms may occur gradually or suddenly as a result of trauma, and they may be difficult to attribute to a particular cause.

The clinical examination may reveal the anatomic locus of the symptoms, but the findings are often not precise in distinguishing other causes of similar symptoms, such as plantar fasciitis, tendinosis, and subtalar and talonavicular synovitis. These problems require different treatments; therefore, imaging studies play an important part in the diagnosis of posterior tibial tendon disorders. In addition, imaging studies are most useful to determine whether the abnormality is limited to the peritendinous area or the tendon itself.

See also Classification and stages in Pathophysiology.

Preferred Examination

Different imaging techniques can be used to assess tendon and tendon sheath abnormalities.^{14,20,21,22,23}

Tendon abnormalities can be evaluated with tenography. This is accomplished with a needle puncture of the tendon sheath.^24,25

Sonography is becoming an increasingly important imaging modality for evaluating musculoskeletal disorders because of its availability, noninvasiveness, lack of ionizing radiation, multiplanar and real-time capabilities, and low cost. Higher-resolution transducers and the dynamic real-time capability of sonography make it attractive for evaluating muscles and tendons. Because of its superficial location, the posterior tibial tendon is particularly amenable to evaluation with sonography.

In the delineation of tendon calcification and retinacular avulsions of bone, CT is superior to MRI. However, in analysis of tendon dislocation both CT and MRI are of nearly equal value

With its superior soft-tissue contrast resolution and multiplanar capabilities, MRI is the imaging procedure of choice for evaluating the musculoskeletal system, particularly in detecting tenosynovitis and in assessing partial and complete ruptures of the tendons. Both MRI and sonography can be used to distinguish tendinosis from peritendinosis. This distinction is important because a more rigorous treatment is needed if the tendon is involved, because it might lead to partial and complete tear.

Imaging also provides insight into the pathophysiology of the disease process. Tendinosis and peritendinosis are often seen together (45% of cases); this observation is readily explained by a common causal mechanism of injury to the 2 sites. The finding of peritendinosis by itself, without tendinosis, is more common (20% of cases) than tendinosis alone without peritendinosis (7%), possibly because the tendon is stronger than the peritendinous tissue and therefore more resistant to injury.

Limitations of Techniques

Plain radiography and bone scintigraphy lack sensitivity.

An inherent drawback of both MRI and sonographic modalities is an inability to further categorize tendon abnormalities. Inhomogeneity of the tendon on MRI could be due to tendinitis, partial tears, degeneration, or other tendinopathies. All these entities fall into a spectrum of pathologic disorders, and determining when one ends and the second begins is difficult. One can speculate that inhomogeneity alone without enhancement is indicative of partial tear or chronic tendinopathy, but those disorders cannot be diagnosed on MRIs, and sonography does not help in resolving this problem.

CT is valuable only when an associated bony abnormality is present; however, tendinous or peritendinous abnormalities are least confidently detected by using imaging.

Enhancement of the tendon and the area around it on MRIs and increased flow on color-flow Doppler sonograms are the most useful features for diagnosing tendinosis and peritendinosis. Other useful, but less specific and less sensitive, criteria are as follows: for tendinosis, a change in signal intensity of the tendon on MRIs and inhomogeneity of the tendon on sonograms; for peritendinosis, increased soft tissue and fluid in the area around the tendon.

In the diagnosis of tendinosis, use of the combined criteria of flow and inhomogeneity of the tendon yields the best positive predictive value (90%) and the best negative predictive value (83%) for sonography, as compared with MRI. The addition of the abnormal size of the tendon as a criterion does not improve the sensitivity, specificity, or predictive values in the diagnosis of tendinosis.

Similarly, in the diagnosis of peritendinosis, the combined criteria of flow and increased soft tissue in the area around the tendon yield the best positive predictive value (89%) and the best negative predictive value (75%) for sonography.

Differential Diagnoses

Ankle, Flexor Hallucis Longus Tendon Injuries
Pes Planus
Plantar Fasciitis

Other Problems to Be Considered

Flat foot (pes planus)
Plantar fasciitis, tendinosis
Subtalar synovitis
Talonavicular synovitis

Radiography

Findings

Routine radiographic findings associated with abnormalities of the tendons and tendon sheaths of the foot and ankle include the following: soft tissue swelling; a change in the contour, calcification, or ossification of a tendon; bone proliferation; fracture fragments; and sesamoid displacement. Soft-tissue swelling and fullness may accompany synovitis, but the finding is not specific (see Image below and Image 16 in Multimedia).

Ankle, tibialis posterior tendon injuries. Lateral plain radiograph of a flat foot resulting from long-standing tibialis posterior tendon rupture.

Radiographically, a dislocated tibialis posterior tendon can be diagnosed by noting the presence of a small avulsion fracture near the insertion of the flexor retinaculum on the medial malleolus.

Tenography

Tenography is a procedure in which the tendon sheath is directly opacified with contrast medium. The peroneal tendon sheath is the first to be studied with tenography.

The frequency of tenography performed throughout the United States and worldwide is not known. However, about half of the cases of tenography are performed to evaluate the tibialis posterior tendon. Although MRI and CT may have replaced tenography in many institutions, tenography still has a role in the management of chronic foot and ankle pain; it is used in verifying that a patient's pain is coming from the tendon sheath, in surgical decision making, and in the injection of therapeutic steroids.

Technique

After the administration of a local anesthetic, a 25-gauge needle is inserted into the tendon. A 10-mL syringe filled with a mixture of contrast material diluted 2:1 with a local anesthetic is attached via flexible tubing. During the gentle injection, the needle is withdrawn until free filling of the tendon sheath is observed under fluoroscopy. The injection continues until the tendon sheath fails to fill at its distal end, until contrast material flows proximally into the fascial sheath around the muscle, or until the patient feels discomfort. Betamethasone has the lowest risk of a flare response after the injection.

Normally, the tendon sheath demonstrates a smooth contour. At the level of the tibial plafond, there is normally extrinisic compression on the tibialis posterior tendon sheath produced by the flexor retinaculum. This should not be confused with pathologic adhesion or stenosis (see Image below and Image 17 in Multimedia).

Ankle, tibialis posterior tendon injuries. Lateral tenogram shows extrinsic compression on tibialis posterior tenograms at the level of the tibial plafond produced by the flexor retinaculum (between arrowheads). This should not to be mistaken for pathologic adhesion or stenosis. Note the injecting needle (arrow).

Ankle, tibialis posterior tendon injuries. Tenogram shows 6-10 sacculations (arrowheads) suggesting moderate tenosynovitis of the tibialis posterior tendon sheath. Note normal narrowing of the tendon sheath (between arrows) overlies the tibial plafond.

Ankle, tibialis posterior tendon injuries. Tenogram shows more than 10 sacculations along the margins of the tibialis posterior tendon sheath suggestive of severe tenosynovitis. Note the defect in the distal tibialis posterior tendon sheath allowing contrast material to pass into the talonavicular joint and the distal subtalar facet (arrows).

Ankle, tibialis posterior tendon injuries. Lateral tenogram depicts a filling defect/mass effect (arrowheads) of the tibialis posterior tendon representing a tear, which was confirmed at surgery.

Ankle, tibialis posterior tendon injuries. Lateral tenogram depicts a mass/filling defect (arrows), which represents a torn tibialis posterior tendon. Note contrast material, which fills the sheaths of both the tibialis posterior tendon and the flexor digitorum longus (arrowheads) tendon.

Computed Tomography

Findings

CT can be used effectively to study the tendons of the foot and ankle.^26,27

Transaxial CT images are the easiest to acquire, and they provide the most useful information, although reformatted transaxial images in the coronal and sagittal planes are occasionally required.

The CT features of a normal tendon include a smooth contour, a size similar to that on the opposite side, a well-defined margin, and attenuation values 75-115 HU (Hounsfield unit) higher than those of the respective muscles. Tenosynovitis is manifest as an enlarged tendon with an inhomogeneous appearance. The surrounding swollen, fluid-containing tendon sheath has a lower attenuation value than that of the tendon itself. Tendon displacement, tethering, or rupture may be evident, and the relationship of the tendon to the adjacent bone is identified readily. Tendon ruptures are associated with partial or complete discontinuity of the fibers and a decrease in the attenuation values (30-50 HU).

Degree of Confidence

Diagnostic difficulties are encountered with CT, owing to beam-hardening artifacts that cause inaccurate assessment of the attenuation values and to the presence of surrounding inflammation that obscures the contour of the tendon and the tendon sheath.

MRI is superior to CT in delineating small amounts of fluid around the tendon and in allowing differentiation of scar tissue from edema and fluid. CT is superior to MRI in demonstrating regions of tendon calcification and avulsion fractures related to the retinacula.

False Positives/Negatives

Rosenburg et al found that CT is sensitive in 90% of cases of tibialis posterior rupture and specific in 100%.²⁸ They defined 3 categories of injury: type 1 is a partially torn bullous or hypertrophied tendon with vertical splits and defects; type 2, partially torn and attenuated; and type 3, complete tendinous disruption with an intratendinous gap. CT has an accuracy of 91% in detecting tendon ruptures.

Magnetic Resonance Imaging

Findings

MRI has been applied to the assessment of the tendons and other structures in the ankle and foot. The tibialis posterior tendon and the Achilles tendon have received the greatest attention.^{29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45}

Technical aspects

The technical aspects of performing MRI of the tibialis posterior tendon are controversial. MRIs can be obtained in the sagittal, coronal, or transaxial (plantar) plane or in a combination of these. The specific plane selected depends on the particular anatomic regions and structures to be evaluated and on the clinical questions involved. The axial plane is optimal; however, some institutions prefer oblique axial imaging perpendicular to the long axis of the tibialis posterior tendon. Sagittal imaging is the secondary plane, with the coronal plane used only as a supplement.

Two sets of axial images are ideal. One set of images should be morphology weighted to optimize the signal-to-noise ratio (see Images below and Images 22-23 in Multimedia). Parameters for this imaging may include the following: sequence, fast spin echo; repetition time/echo time, 4000/35; echo train length, 4; field of view, 14; and matrix, 256 x 256. Another set of images should be T2-weighted by using fat-suppression and fast spin-echo protocols with a repetition time/echo time of 6000/75.

Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the dome of the talus showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat.

Ankle, tibialis posterior tendon injuries. Same patient as in Image 22 in Multimedia; image taken at a slightly distal axial plane showing the progression of tibialis posterior tendon damage.

Sagittal images should be T1-weighted (see Images below and Images 24-25 in Multimedia) and acquired with either T2-weighting with fat suppression or a short-tau inversion recovery (STIR) sequence.

Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted image showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat at and below the medial malleolus.

Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted image showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat at and below the medial malleolus. Note straightening with loss of normal curvature of the tibialis posterior tendon at and below the medial malleolus. Same patient as in Image 24 in Multimedia.

Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted MRI in an adult healthy man shows a low-signal-intensity tibialis posterior tendon (open arrow). Note the normal smooth curve that the tibialis posterior tendon makes as it extends from the medial malleolus.

Ankle, tibialis posterior tendon injuries. Same patient as in Image 5 in Multimedia; sagittal T2-weighted fat-suppressed MRI in an adult healthy man shows a low-signal-intensity tibialis posterior tendon (open arrow).

Ankle, tibialis posterior tendon injuries. Sagittal proton density MRI in a healthy adult man reveals the normal smooth malleolar curve of the tibialis posterior tendon (open arrows).

Ankle, tibialis posterior tendon injuries. Axial STIR (short-tau inversion recovery) MRI in a woman with tendon dysfunction and subtendinous edema. Image reveals edema in the medial malleolus related to tibialis posterior tendon dysfunction (open arrow).

Ankle, tibialis posterior tendon injuries. Coronal T2-weighted image showing absence of the tibialis posterior tendon due to complete tear with fluid signal filling the tendon sheath and soft tissue edema replacing the surrounding subcutaneous fat.

Ankle, tibialis posterior tendon injuries. Coronal T2-weighted image (same patient as in Image 30 in Multimedia, slightly posterior planes) showing absence of the tibialis posterior tendon due to complete tear with fluid signal filling the tendon sheath and soft tissue edema replacing the surrounding subcutaneous fat.

Contrast material is useful only in some patients. Contrast material can be used when nonenhanced MRIs show subtle or no findings suggestive of abnormality but when the clinician suspects an abnormality of the tibialis posterior tendon. Moreover, contrast material can be used for the evaluation of suspected synovitis, infection, or inflammatory arthritis. Lastly, contrast material is helpful for the assessment of insertional tendinitis (see Image below and Image 32 in Multimedia).

Ankle, tibialis posterior tendon injuries. Axial contrast-enhanced fat-suppressed MRI in a middle-aged man with synovitis and interstitial tear reveals excessive contrast enhancement around the tibialis posterior tendon (open arrow) in the region of the medial malleolus; this finding is consistent with synovitis. Enhancement is also seen in the tibialis posterior tendon; this is suggestive of an interstitial tear.

General findings

On MRIs, the tibialis posterior tendon is normally black without any internal signal intensity. The exception to this lack of signal intensity is the result of the magic-angle artifact (see Image below and Image 33 in Multimedia) because the tibialis posterior tendon curves around the medial malleolus (see Image 11 and Images 26-28). In comparison with the Achilles tendon, the distal tibialis posterior tendon has no normal internal signal intensity. However, the signal intensity varies distally; the variations are related to volume averaging of the spring ligament (extremely distal), the tibial navicular, and the tibiotalar components of the deltoid ligament (slightly more proximal) (see Image below and Image 34 in Multimedia).

Ankle, tibialis posterior tendon injuries.Same patient as in Image 38 in Multimedia; axial T2-weighted fat-suppressed MRI in a young adult man. Note that internal signal intensity in tibialis posterior tendon fades on long-TE images. This finding is consistent with magic-angle artifact (open arrow).

Ankle, tibialis posterior tendon injuries. MRI T1-weighted in an adult man with a normal tibialis posterior tendon. Image shows the close proximity of the tibialis posterior tendon (arrowhead); spring ligament (curved arrow); and tibial navicular ligament (open arrow), which gives the appearance of a thickened distal tibialis posterior tendon.

In common with the findings derived from ultrasonography and CT, the major MRI finding of tenosynovitis is abnormal accumulation of fluid within the tendon sheath. This fluid has low signal intensity on T1-weighted spin-echo images and high signal intensity on T2- and STIR-weighted images (see Image below and Image 35 in Multimedia). Pannus and scar formation around a tendon are characterized by intermediate signal intensity on T1-weighted spin-echo images and intermediate-to-high signal intensity on T2-weighted spin-echo images (see Images below and Images 36-37 in Multimedia).

Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Images 36 and 37 (few months after conservative management); axial STIR MRI in an adult woman with peritendinosis. Image shows enhancement of the peritendinous area (open arrow) with slight increase in fluid signal.

Ankle, tibialis posterior tendon injuries. Axial T1-weighted MRI of the ankle in a young adult woman with peritendinosis shows increased soft tissue with mixed signal intensity in the peritendinous area (open arrow) in addition to tendon thickening.

Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Image 36; axial T2-weighted MRI in a young woman with peritendinosis reveals mixed signal intensity and increased peritendinous soft tissue (open arrow).

Tendinitis is accompanied by focal areas of high signal intensity within the substance of the tendon on proton density– and T2-weighted spin-echo images (see Image below and Image 38 in Multimedia). With chronic tendinitis, the tendon is enlarged and of low signal intensity in both T1-weighted and T2-weigted spin-echo images (see Image 2).

Ankle, tibialis posterior tendon injuries. Axial T1-weighted MRI in a young adult man shows diffuse internal signal in the tibialis posterior tendon (arrow).

The MRI appearance of paratendonitis is similar to that seen in the Achilles tendon, with partially circumferential areas of high signal intensity located distally around the tibialis posterior tendon. This signal intensity is usually slightly less than that of fluid. Because normally no fluid is present distally around the tibialis posterior tendon on MRIs, the term synovitis should be used to describe this disorder only when it occurs more proximally (see Image 36). If apparent synovitis is seen distally, it is anatomically a paratendinitis, and images often reveal fluid with signal intensity slightly lower than what is typical for bland fluid (see Image 2). At this stage of the disorder, the tendon itself is normal and should not show intratendinous hypersensitivity. Tibialis posterior tendon disorders manifested by synovitis are often acutely symptomatic.

Although degeneration is histologically common, signal abnormalities caused by degeneration are infrequently seen on MRIs. In most patients, degeneration occurs with an apparently normal tibialis posterior tendon, as shown on MRIs.

In a transitional stage of tibialis posterior tendon disorder, microscopic and eventually macroscopic tears of the tendon fiber occur. Few partial tears are seen on MRIs, although most are seen on sonograms. On MRIs, subtle focal areas of high signal intensity may be visible in the tendon. At surgery, the disruption is often more extensive than it appears on MRIs. Therefore, what may appear as synovitis or tendinitis on images may in fact be a partial tear.

Tendon ruptures may be acute or chronic and partial or complete. Recent tendon tears frequently reveal regions of increased signal intensity on T2-weighted spin-echo images and on certain gradient-echo images, owing to the presence of edema and hemorrhage. Remote tendon tears generally do not have these high-signal-intensity characteristics, owing to the presence of scar tissue.

Patterns of tendon tears

With regard to the extent of tendon tears, 3 MRI patterns have been described: type 1, type 2, and type 3.

Type 1 tears are partial tendon ruptures with tendon hypertrophy. The involved tendon appears hypertrophied or bulbous, and it reveals heterogeneous signal intensity. Focal areas of increased signal intensity are noted within its substance. The MRI pattern corresponds to a surgically evident, partially torn tendon with vertical splits and defects. The presence of an interstitial tear with a longitudinal split of the tibialis posterior tendon is also common (see Images below and Image 7 and Images 39-43 in Multimedia). This is the only type of tibialis posterior tendon disorder that appears with high signal intensity on T2-weighted MRIs, and it is almost invariably associated with synovitis.

Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the talus showing thickening of the tibialis posterior tendon containing subtle foci of increased signal intensity with adjacent soft tissue edema replacing the surrounding subcutaneous fat.

Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the talus showing thickening of the tibialis posterior tendon containing subtle foci of increased signal intensity with adjacent soft tissue edema replacing the surrounding subcutaneous fat.

Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the talus showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat. Note the enlarged tibialis posterior tendon relative to the flexor digitorum, flexor hallucis, and tibialis anterior tendons. Same patient as in Image 40 in Multimedia.

Ankle, tibialis posterior tendon injuries. T1-weighted MRI of the ankle. Coronal image shows thickening of the tibialis posterior tendon (arrowhead) with increased internal signal intensity. There is marrow edema immediately subjacent to the medial malleolus seen on the T2-weighted images.

Ankle, tibialis posterior tendon injuries. Axial intermediate-weighted MRI in a middle aged man with an interstitial tendon tear. Image reveals an enlarged tibialis posterior tendon with several linear regions of signal intensity that split tibialis posterior tendon into fascicles (open arrow).

Type 2 tears are partial tendon ruptures with tendon attenuation. The involved tendon is stretched and attenuated in size; the MRI findings correspond to those found at surgery (see Image 8).

Type 3 tears are complete tendon ruptures with tendon retraction. The involved tendon is discontinuous; in some cases, a gap is evident that is filled with fluid, fat, or scar tissue, depending on the age of the tear. The size of the gap is variable both on MRI and at surgery, and this gap reflects the degree of tendon retraction. A tibialis posterior tendon tear with a gap is unusual. Usually, what is seen is severe thinning of the tibialis posterior tendon with thin residual threads that appear as a dysfunctional tendon during clinical examination.

Additionally, involvement of the spring ligament may be seen with severe tibialis posterior tendon tears.

Tendon subluxation or dislocation is easily detected with MRI, as with CT, owing to an abnormal relationship of the tendon with the adjacent tissues. The tendon itself may be enlarged or partially torn, and associated soft-tissue and bony injury may be evident (see Images below and Images 44-45 in Multimedia).

Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in an adult man with a dislocated tibialis posterior tendon. Image reveals that the tibialis posterior tendon is dislocated anteriorly, out of its groove (arrow). Note how the normal flexor digitorum tendon (open arrow) remains posterior to tibia, while the tibialis posterior tendon is subluxed medially and anteriorly.

Ankle, tibialis posterior tendon injuries. Axial proton density–weighted MRI in a middle-aged woman with a subluxed tendon. Image reveals that the tibialis posterior tendon (open arrow) is slightly subluxed medially, out of its groove (arrowhead).

Exceptions to general findings

With minor exceptions, the normal tendons in the ankle and foot are homogeneous and of low signal intensity with all MRI sequences. They generally are equal in size on the 2 sides of the body, and they have a smooth contour. However, some exceptions to these general rules include the following: magic-angle effect, tenosynovial fluid, bulbous tendon insertion sites, and tendon striations.

Magic-angle effect

As indicated earlier, increased signal intensity may be seen in normal tendons oriented obliquely with respect to the main magnetic field; this effect is greatest when this orientation is at 55° to that of the magnetic field (see Image 13 and Image 33). This effect is greater when the MRI involves a spin-echo technique with short echo times or a gradient-echo technique.

The tibialis posterior tendon approximates this orientation at its site of attachment to the navicular bone, resulting in a normal appearance of increased signal intensity or heterogeneous signal intensity in this area. This alteration in signal intensity may be accentuated by volume averaging of different signal intensities derived from the joint capsule and fat in this region. Furthermore, repeating the MRI examination with a foot in plantar flexion diminishes or eliminates this magic-angle phenomenon.

Tenosynovial fluid

The differentiation of thickened tendons from one surrounded by a fluid-filled synovial sheath is difficult on T1-weighted spin-echo MRIs. Moreover, the presence of small or even moderate amounts of fluid within a tendon sheath, by itself, is not diagnostic of an abnormality, because such fluid is seen in asymptomatic persons. Tenosynovial fluid is more common in flexor tendons, as compared with extensor tendons, and this may be particularly prominent around the flexor hallucis longus tendon.

Bulbous tendon insertion sites

Insertion sites of tendons may appear bulbous (see Image 26 and Image 28). This appearance is perhaps related to volume averaging of their signal intensity with that of adjacent cortical bone. This appearance can simulate that of a tendon disruption, particularly one of the tibialis posterior tendons.

Tendon striations

When 3-dimensional gradient-recalled-echo MRIs are obtained, longitudinal lines of intermediate signal intensity may be noted in the distal portion of the tibialis posterior tendon. These lines probably represent branches of the tendon, although their appearance may simulate that of a tendon tear.

Secondary signs of tibialis posterior tendon dysfunction

The abnormal mechanics of the tibialis posterior tendon can result in anatomic changes that appear on MRIs. Although most MRI examinations are not performed while the tendons are bearing weight, MRI is a tomographic technique, and subtle mechanical disturbances may be apparent. These secondary signs can increase the diagnostic confidence in describing subtle tibialis posterior tendon disorders. Most of these signs are not pathognomonic of tibialis posterior tendon dysfunction, because they can be seen with other causes of pes planus and foot disorders. In addition, reducible and nonreducible deformities are distinguished clinically.

On MRI, the only distinction is that nonreducible deformities tend to be more severe, with secondary osteoarthritic changes. Excessive plantar flexion of the talus results in a mechanical disturbance called talonavicular fault. On the sagittal MRI on which the base of the first metatarsal is visible, a long axis is drawn on the talus and extended into the navicular. The failure of this line to divide the navicular into equal superoinferior parts, with the line positioned inferiorly, is a manifestation of the talonavicular fault and hence a dysfunctional tibialis posterior tendon (see Image below and Image 46 in Multimedia).

Ankle, tibialis posterior tendon injuries. Sagittal T2-weighted MRI in a middle-aged woman with a talonavicular fault. Image reveals that a line drawn along the long axis of talus extends inferiorly rather than bisecting the navicular.

Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in a middle-aged man with talonavicular unroofing. Image shows unroofing of the upper aspect of the talus with the navicular subluxed laterally (arrowhead), exposing the medial talonavicular head; this is a secondary sign of tibialis posterior tendon insufficiency. There is also an interstitial tear of the tibialis posterior tendon (open arrow).

Additionally, a heel valgus as revealed on coronal images is an indirect sign of a tibialis posterior tendon tear (see Image below and Image 48 in Multimedia). The long axes of the calcaneus and the tibia normally subtends an angle with 0-6° of valgus.

Ankle, tibialis posterior tendon injuries. Coronal T1-weighted MRI in an adult man with tendon dysfunction and heel valgus. Image reveals heel valgus. Lines of reference go through the long axes of the tibia and calcaneus.

Marrow abnormalities

Bone marrow findings related to tibialis posterior tendon disorders include the accessory navicular, the cornuate navicular (see Images below and Image 49 in Multimedia), and marrow edema. The first 2 entities lead to a more proximal insertion of the tibialis posterior tendon, reducing the curve around the malleolus. This straightening of the curve leads to focal attritional wear and tear of the tibialis posterior tendon (see Images below and Image 50 and Image 51 in Multimedia).

Ankle, tibialis posterior tendon injuries. Axial proton density weighted MRI in an adult man at risk for tibialis posterior dysfunction. Image shows hypertrophy of navicular tubercle (open arrow), consistent with a cornuate navicular.

Ankle, tibialis posterior tendon injuries. Sagittal T2-weighted MRI in a man at risk for posterior tibialis dysfunction reveals accessory navicula (a). Note the straight line (instead of the normal smooth curve) that the tibialis posterior tendon makes as it extends from the medial malleolus. This abnormality causes a focal point of friction at the medial malleolus (open arrow).

Ankle, tibialis posterior tendon injuries. Same patient as in Image 50 in Multimedia; axial intermediate-weighted MRI in a young adult at risk for tibialis posterior tendon dysfunction shows the accessory navicular with low-signal-intensity synchondrosis (open arrow).

Ankle, tibialis posterior tendon injuries. T2-weighted fat-suppressed MRI of the ankle in an adult woman with several months' history of medial ankle pain and tibialis posterior tendinopathy that is associated with subtendinous bone marrow edema of the medial malleolus. Axial image shows thickening of the tibialis posterior tendon (arrow). Note the marrow edema immediately subjacent to the medial malleolus (open arrow).

Ankle, tibialis posterior tendon injuries. Same patient as in Image 52 in Multimedia; T2-weighted fat-suppressed fast MRI of the ankle. Sagittal image shows thickening of the tibialis posterior tendon with increased internal signal intensity (arrow). Note the marrow edema immediately subjacent to the medial malleolus (open arrow).

The development of a pseudoarthrosis between the accessory navicular and the native navicular is related to the tibialis posterior tendon. A chronic tibialis posterior tendon pull can lead to fracture of the normal synchondrosis. On MRIs, fluid is visible between the 2 bones, with kissing marrow edema on either side of the pseudoarthrosis (see Image below and Image 54 in Multimedia).

Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in an adult man with accessory navicular pseudoarthrosis. Image reveals fluid between the navicular and accessory navicular; this is consistent with pseudoarthritis. Also note the edema in both bones (open arrows); this reflects altered mechanics.

On MRIs, the tibialis posterior tendon is seen subluxed anteriorly and medially, and it is seen as the most medial aspect of the tibia rather than behind it (see Image 44). Although a tibialis posterior tendon dislocation is uncommon, this is the second most common dislocation of the ankle tendons, after peroneal dislocations. Repetitive transient subluxation may also be part of the pathophysiology of more typical tibialis posterior tendon tears. The retromalleolar groove is usually shallow in patients with a tibialis posterior tendon dislocation, and the retinaculum may be visibly stripped off or torn. Infrequently, a related tear in the tendon is discovered.

Degree of Confidence

MRI is the current standard imaging technique for the diagnosis of foot and ankle problems. When inhomogeneity of the tendon is seen on MRIs, it could be due to tendinitis, a partial tear, degeneration, or another tendinopathy. All these entities fall into a spectrum of disorders, and determining when one ends and another begins is difficult. Hence, all these entities should be considered in the differential diagnosis.

While applying their classification, Rosenberg et al found MRI for diagnosing tendon ruptures to be sensitive in 95% of cases and specific in 100%. MRI has a 96% accuracy in detecting tendon rupture. The overall accuracy, which reflects a percentage of cases correctly diagnosed, as well as those correctly classified, was 59% for CT and 73% for MRI.

Ultrasonography

Findings

High-resolution sonography has gained acceptance for musculoskeletal abnormalities. It has the advantages of ready availability, noninvasiveness, and low cost.^{37,38,46,47,48,49,50,51,52}

On sonograms, the posterior tibial tendon normally shows homogeneous echogenic longitudinal fibers (see Images below and Image 9 and Images 55-56 in Multimedia). No flow is seen in or around the tendon on color-flow Doppler sonograms. Minimal fluid is often seen adjacent to the tendon.

Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Image 55; longitudinal sonogram in a young healthy woman shows minimal fluid (open arrow) seen adjacent to distal tibialis posterior tendon.

Ankle, tibialis posterior tendon injuries. Longitudinal sonogram in a young healthy woman shows a normal tibialis posterior tendon (between calipers). Arrow points to the medial malleolus.

Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Images 9 and 55; transverse sonogram in a young healthy woman shows a normal tibialis posterior tendon (between calipers). Open arrow points to the flexor digitorum longus tendon adjacent to tibialis posterior tendon.

Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Image 58; transverse color Doppler sonogram of tibialis posterior tendon in a young adult with tendinosis and peritendinosis. Image shows peritendinous (open arrow) and intratendinous (arrowheads) flow.

Ankle, tibialis posterior tendon injuries. Same patient as in Image 39 in Multimedia; transverse sonogram in a middle-aged woman with tendinosis shows an enlarged inhomogeneous tibialis posterior tendon (between calipers).

Ankle, tibialis posterior tendon injuries. Transverse sonogram in a young adult woman with peritendinosis (open arrow points to low echogenicity in peritendinous area).

Other than size, the 2 MRI criteria used for the diagnosis of tendinosis are contrast enhancement and the abnormal signal intensity of the tendon. These criteria are compared with color Doppler findings of flow in the tendon and with the sonographic inhomogeneity of the tendon.

For the diagnosis of peritendinosis, the criteria used for MRI are contrast enhancement of the peritendinous tissues and an increase in the amount of soft tissue and fluid in the peritendinous area. The corresponding criteria used for sonography are flow in the peritendinous area on color Doppler images and an increase in the amount of soft tissue and fluid in the peritendinous area.

Technique

Sonography is performed by using a small-parts 10-MHz transducer. The patient is placed in a prone oblique position with his or her ankle slightly elevated on a rolled towel so that the posterior tibial tendon and flexor digitorum longus tendon can be optimally evaluated.

The posterior tibial tendon is first identified just posterior to the medial malleolus. The tendon is followed along its entire length to the insertion into the navicular tuberosity. The anteroposterior diameter is measured on the longitudinal view of the posterior tibial tendon at approximately 1 cm distal to the tip of the medial malleolus. The transducer is then turned 90°, and transverse scans and measurements of the transverse diameter of the posterior tibial tendon are obtained.

The flexor digitorum longus tendon (which lies slightly posterior to the posterior tibial tendon) is then evaluated in a similar manner. Anteroposterior and transverse diameters of the posterior tibial tendon and the flexor digitorum longus tendon are measured 1 cm distal to the medial malleolus. Color and power Doppler sonography are then used to evaluate both tendons and the area around the tendon. The Doppler gain is set so that no flow is present in the cortical bone.

Degree of Confidence

Enhancement of the tendon and peritendinous area on MRIs and increased flow on color-flow Doppler sonograms are the most useful features for diagnosing tendinosis and peritendinosis.

Other useful, but less specific and sensitive, criteria are as follows: for tendinosis, a change in signal intensity of the tendon on MRI and inhomogeneity of the tendon on sonography; for peritendinosis, increased soft tissue and fluid in the peritendinous area.

In the diagnosis of tendinosis, use of the combined criteria of flow and inhomogeneity of the tendon yield the best positive predictive value (90%) and the best negative predictive value (83%) for sonography compared with MRI. The addition of the abnormal size of the tendon as a criterion does not improve the sensitivity, specificity, or predictive values in the diagnosis of tendinosis.

Similarly, in the diagnosis of peritendinosis, the combined criteria of flow and increased soft tissue in the area around the tendon yields the best positive predictive value (89%) and the best negative predictive value (75%) for sonography.

Nuclear Imaging

Findings

Nuclear medicine provides a number of sensitive techniques for the evaluation of foot pain. However, the techniques are not always specific. In subacute or chronic injuries in which prolonged pain is unexplained, the 3-phase bone scan may play a significant role.^53,54

Bone scanning may be useful in differentiating soft-tissue pathology from bone pathology, and being a sensitive test, it may indicate the region that needs further specific radiologic examination. It may also indicate the clinical significance of a radiologic finding.

Careful attention to the technique enhances the efficiency of bone scintigraphy, and single-photon emission compute tomography (SPECT) allows better investigation of the hindfoot. With improved technique and instrumentation, the finding of a focal abnormality in the ankle or foot on bone scintigraphy is no longer sufficient. More precise information about perfusion, the blood pool, and the specific location of a lesion can be obtained with high-resolution and tomographic images.

Degree of Confidence

Nuclear medicine studies must be interpreted with knowledge of the patient's history and symptoms and with close correlation with the plain radiographic findings.

Angiography

Findings

Angiography is not used.

False Positives/Negatives

Intervention

Early diagnosis and treatment may prevent considerable disability and surgery.

The therapeutic effect of tenography is likely a combination of local anesthesia, the anti-inflammatory effect of the steroids, and the actual mechanical dilatation of the tendon sheath due to fluid placed in the sheath. Patients with stenosing tenosynovitis may not receive a therapeutic effect from the tenography if the injected liquid does not extend through the stenotic area. Subsequently, patients with more advanced disease may need surgery. Almost half of the patients, regardless of the radiographic appearance of the tenosynovitis, have long-term complete or near-complete relief of symptoms after the therapeutic injection of steroids, contrast material, and local anesthesia during tenography.^{55,56,57,58,59}

Complications include the loss of skin pigmentation. This almost always occurs in dark skin. Transient bruising, infection, and partial paresthesia can occur. Tibialis posterior tendon rupture as a complication of steroid injection is reported in less than 1% of cases. Therefore, to decrease the likelihood of tendon rupture, patients should refrain from participating in sports for 6 weeks. The use of a removable walking brace or a cast for 6 weeks may be prudent after a tendon injection. Moreover, tenography, and particularly steroid injection, is not recommended in cases of a suspected tendon rupture.

The extent of the tendon tear, as well as its location, influences the type of surgical repair that may be attempted. A small focal area of tendon rupture may be treated with surgical resection and end-to-end tendon anastomosis, and a large area of tendon rupture may require side-to-side tendon anastomosis. A large tendon rupture with tendon retraction may preclude direct anastomosis of the torn ends of the tendon; in some cases, arthrodesis is required to prevent further foot deformities.

Medicolegal Pitfalls

• Missing the diagnosis
• Misdiagnosing the condition with one of the other differential diagnoses
• Difficulty in interpreting postoperative imaging studies, especially images of recurrent partial tears

Multimedia

Media file 1: Ankle, tibialis posterior tendon injuries. Axial T2-weighted fat-suppressed MRI in an adult man with peritendinous edema. Image reveals reactive marrow edema (open arrow) under the tibialis posterior tendon groove; this is caused by tibialis posterior tendon dysfunction.

Media file 2: Ankle, tibialis posterior tendon injuries. Sagittal fast short-tau inversion recovery (STIR) MRI in a middle-aged woman with insertional tendonitis. Image reveals fluid and diffuse flocculent signal intensity in the distal tibialis posterior tendon; this is consistent with insertional tendonitis (open arrow). Note the adjacent soft-tissue edema. Also note the longitudinal areas of high signal intensity in the tendon; this finding is consistent with an interstitial tear.

Media file 3: Ankle, tibialis posterior tendon injuries. Axial T1-weighted MRI in an adult woman with tibialis posterior tenosynovitis. Image reveals the speckled internal signal intensity of the tibialis posterior tendon (open arrow).

Media file 4: Ankle, tibialis posterior tendon injuries. Same patient as in Picture 6; STIR-weighted MRI in an adult woman with tibialis posterior tenosynovitis. The signal intensity is more intense on this image than on others and it is associated with synovitis (open arrow).

Media file 5: Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in a middle-aged woman with an atrophic tear. Image reveals an attenuated, threadlike, tibialis posterior tendon (open arrow) consistent with an atrophic-type tear.

Media file 6: Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in a middle-aged woman with an atrophic tendon and a tibial spur. Image reveals a thinned tibialis posterior tendon (open arrow) that is adjacent to a spur (arrowhead); this finding is characteristic of tibialis posterior tendon dysfunction.

Media file 7: Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in a middle-aged man with a hypertrophic tear reveals an enlarged tendon (open arrow) adjacent to the deltoid ligament (arrow). This tibialis posterior tendon is roughly 3-4 times the size of the adjacent flexor hallucis and flexor digitorum tendons; this finding is consistent with hypertrophic dysfunction.

Media file 8: Ankle, tibialis posterior tendon injuries. Sagittal short-tau inversion recovery MRI in a middle-aged man with mixed hypertrophic and atrophic tendon tear. Image reveals a focal tear of the submalleolar (arrowhead) with tendon thinning. Retracted fibers cause spurious tendon thickening (open arrow).

Media file 9: Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Image 55; longitudinal sonogram in a young healthy woman shows minimal fluid (open arrow) seen adjacent to distal tibialis posterior tendon.

Media file 10: Ankle, tibialis posterior tendon injuries. Drawing shows the relationship of the tibialis posterior tendon to the remainder of the tarsal tunnel. Note the relative sites and the distal extent of tendon sheaths in black. Also note that the flexor hallucis and flexor digitorum tendons cross distally at the knot of Henry (straight arrow). Last, note the tibial artery and nerve (curved arrow) between the flexor digitorum longus tendon and the flexor hallucis longus tendon in the tarsal tunnel. ATT, anterior tibialis tendon; FDL, flexor digitorum longus tendon; FHL, flexor hallucis longus tendon; FR, flexor retinaculum; and PTT, tibialis posterior tendon.

Media file 11: Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted MRI in a middle-aged woman with tibialis posterior tendon tear reveals straightening of normal malleolar curve. The patient has a markedly thickened tibialis posterior tendon (open arrow) with a large segment of internal signal intensity (white arrows).

Media file 12: Ankle, tibialis posterior tendon injuries. Drawing shows the complex insertions of the tibialis posterior tendon beneath the undersurface of the foot with the muscle dissected away. Note the main slip inserting onto the tubercle of the navicular. Also note the close anatomic relationship of the distal tendon, spring ligament, and distal deltoid ligament. C, calcaneus; N, navicular; PTT, tibialis posterior tendon.

Media file 13: Ankle, tibialis posterior tendon injuries. Axial unenhanced T1-weighted MRI in a healthy adult male shows normal low-signal intensity tibialis posterior (long arrow) and flexor digitorum longus (short arrow) tendons; note the relative sizes.

Media file 14: Ankle, tibialis posterior tendon injuries. Same patient as in Picture 13; axial unenhanced STIR weighted MRI in a healthy adult male shows normal low-signal intensity tibialis posterior (long arrow) and flexor digitorum longus (short arrow) tendons; note the relative sizes.

Media file 15: Ankle, tibialis posterior tendon injuries. T1-weighted fat-suppressed MRI in a young healthy man shows the ratio of the sizes of the tibialis posterior tendon (open arrow) and the flexor digitorum tendon (solid arrow). Also note how the normal tibialis posterior tendon is slightly smaller than the summated peroneal tendons (arrowhead).

Media file 16: Ankle, tibialis posterior tendon injuries. Lateral plain radiograph of a flat foot resulting from long-standing tibialis posterior tendon rupture.

Media file 17: Ankle, tibialis posterior tendon injuries. Lateral tenogram shows extrinsic compression on tibialis posterior tenograms at the level of the tibial plafond produced by the flexor retinaculum (between arrowheads). This should not to be mistaken for pathologic adhesion or stenosis. Note the injecting needle (arrow).

Media file 18: Ankle, tibialis posterior tendon injuries. Tenogram shows 6-10 sacculations (arrowheads) suggesting moderate tenosynovitis of the tibialis posterior tendon sheath. Note normal narrowing of the tendon sheath (between arrows) overlies the tibial plafond.

Media file 19: Ankle, tibialis posterior tendon injuries. Tenogram shows more than 10 sacculations along the margins of the tibialis posterior tendon sheath suggestive of severe tenosynovitis. Note the defect in the distal tibialis posterior tendon sheath allowing contrast material to pass into the talonavicular joint and the distal subtalar facet (arrows).

Media file 20: Ankle, tibialis posterior tendon injuries. Lateral tenogram depicts a filling defect/mass effect (arrowheads) of the tibialis posterior tendon representing a tear, which was confirmed at surgery.

Media file 21: Ankle, tibialis posterior tendon injuries. Lateral tenogram depicts a mass/filling defect (arrows), which represents a torn tibialis posterior tendon. Note contrast material, which fills the sheaths of both the tibialis posterior tendon and the flexor digitorum longus (arrowheads) tendon.

Media file 22: Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the dome of the talus showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat.

Media file 23: Ankle, tibialis posterior tendon injuries. Same patient as in Image 22 in Multimedia; image taken at a slightly distal axial plane showing the progression of tibialis posterior tendon damage.

Media file 24: Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted image showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat at and below the medial malleolus.

Media file 25: Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted image showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat at and below the medial malleolus. Note straightening with loss of normal curvature of the tibialis posterior tendon at and below the medial malleolus. Same patient as in Image 24 in Multimedia.

Media file 26: Ankle, tibialis posterior tendon injuries. Sagittal T1-weighted MRI in an adult healthy man shows a low-signal-intensity tibialis posterior tendon (open arrow). Note the normal smooth curve that the tibialis posterior tendon makes as it extends from the medial malleolus.

Media file 27: Ankle, tibialis posterior tendon injuries. Same patient as in Image 5 in Multimedia; sagittal T2-weighted fat-suppressed MRI in an adult healthy man shows a low-signal-intensity tibialis posterior tendon (open arrow).

Media file 28: Ankle, tibialis posterior tendon injuries. Sagittal proton density MRI in a healthy adult man reveals the normal smooth malleolar curve of the tibialis posterior tendon (open arrows).

Media file 29: Ankle, tibialis posterior tendon injuries. Axial STIR (short-tau inversion recovery) MRI in a woman with tendon dysfunction and subtendinous edema. Image reveals edema in the medial malleolus related to tibialis posterior tendon dysfunction (open arrow).

Media file 30: Ankle, tibialis posterior tendon injuries. Coronal T2-weighted image showing absence of the tibialis posterior tendon due to complete tear with fluid signal filling the tendon sheath and soft tissue edema replacing the surrounding subcutaneous fat.

Media file 31: Ankle, tibialis posterior tendon injuries. Coronal T2-weighted image (same patient as in Image 30 in Multimedia, slightly posterior planes) showing absence of the tibialis posterior tendon due to complete tear with fluid signal filling the tendon sheath and soft tissue edema replacing the surrounding subcutaneous fat.

Media file 32: Ankle, tibialis posterior tendon injuries. Axial contrast-enhanced fat-suppressed MRI in a middle-aged man with synovitis and interstitial tear reveals excessive contrast enhancement around the tibialis posterior tendon (open arrow) in the region of the medial malleolus; this finding is consistent with synovitis. Enhancement is also seen in the tibialis posterior tendon; this is suggestive of an interstitial tear.

Media file 33: Ankle, tibialis posterior tendon injuries.Same patient as in Image 38 in Multimedia; axial T2-weighted fat-suppressed MRI in a young adult man. Note that internal signal intensity in tibialis posterior tendon fades on long-TE images. This finding is consistent with magic-angle artifact (open arrow).

Media file 34: Ankle, tibialis posterior tendon injuries. MRI T1-weighted in an adult man with a normal tibialis posterior tendon. Image shows the close proximity of the tibialis posterior tendon (arrowhead); spring ligament (curved arrow); and tibial navicular ligament (open arrow), which gives the appearance of a thickened distal tibialis posterior tendon.

Media file 35: Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Images 36 and 37 (few months after conservative management); axial STIR MRI in an adult woman with peritendinosis. Image shows enhancement of the peritendinous area (open arrow) with slight increase in fluid signal.

Media file 36: Ankle, tibialis posterior tendon injuries. Axial T1-weighted MRI of the ankle in a young adult woman with peritendinosis shows increased soft tissue with mixed signal intensity in the peritendinous area (open arrow) in addition to tendon thickening.

Media file 37: Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Image 36; axial T2-weighted MRI in a young woman with peritendinosis reveals mixed signal intensity and increased peritendinous soft tissue (open arrow).

Media file 38: Ankle, tibialis posterior tendon injuries. Axial T1-weighted MRI in a young adult man shows diffuse internal signal in the tibialis posterior tendon (arrow).

Media file 39: Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the talus showing thickening of the tibialis posterior tendon containing subtle foci of increased signal intensity with adjacent soft tissue edema replacing the surrounding subcutaneous fat.

Media file 40: Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the talus showing thickening of the tibialis posterior tendon containing subtle foci of increased signal intensity with adjacent soft tissue edema replacing the surrounding subcutaneous fat.

Media file 41: Ankle, tibialis posterior tendon injuries. Axial T1-weighted image at the level of the talus showing thickening of the tibialis posterior tendon with adjacent soft tissue edema replacing the surrounding subcutaneous fat. Note the enlarged tibialis posterior tendon relative to the flexor digitorum, flexor hallucis, and tibialis anterior tendons. Same patient as in Image 40 in Multimedia.

Media file 42: Ankle, tibialis posterior tendon injuries. T1-weighted MRI of the ankle. Coronal image shows thickening of the tibialis posterior tendon (arrowhead) with increased internal signal intensity. There is marrow edema immediately subjacent to the medial malleolus seen on the T2-weighted images.

Media file 43: Ankle, tibialis posterior tendon injuries. Axial intermediate-weighted MRI in a middle aged man with an interstitial tendon tear. Image reveals an enlarged tibialis posterior tendon with several linear regions of signal intensity that split tibialis posterior tendon into fascicles (open arrow).

Media file 44: Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in an adult man with a dislocated tibialis posterior tendon. Image reveals that the tibialis posterior tendon is dislocated anteriorly, out of its groove (arrow). Note how the normal flexor digitorum tendon (open arrow) remains posterior to tibia, while the tibialis posterior tendon is subluxed medially and anteriorly.

Media file 45: Ankle, tibialis posterior tendon injuries. Axial proton density–weighted MRI in a middle-aged woman with a subluxed tendon. Image reveals that the tibialis posterior tendon (open arrow) is slightly subluxed medially, out of its groove (arrowhead).

Media file 46: Ankle, tibialis posterior tendon injuries. Sagittal T2-weighted MRI in a middle-aged woman with a talonavicular fault. Image reveals that a line drawn along the long axis of talus extends inferiorly rather than bisecting the navicular.

Media file 47: Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in a middle-aged man with talonavicular unroofing. Image shows unroofing of the upper aspect of the talus with the navicular subluxed laterally (arrowhead), exposing the medial talonavicular head; this is a secondary sign of tibialis posterior tendon insufficiency. There is also an interstitial tear of the tibialis posterior tendon (open arrow).

Media file 48: Ankle, tibialis posterior tendon injuries. Coronal T1-weighted MRI in an adult man with tendon dysfunction and heel valgus. Image reveals heel valgus. Lines of reference go through the long axes of the tibia and calcaneus.

Media file 49: Ankle, tibialis posterior tendon injuries. Axial proton density weighted MRI in an adult man at risk for tibialis posterior dysfunction. Image shows hypertrophy of navicular tubercle (open arrow), consistent with a cornuate navicular.

Media file 50: Ankle, tibialis posterior tendon injuries. Sagittal T2-weighted MRI in a man at risk for posterior tibialis dysfunction reveals accessory navicula (a). Note the straight line (instead of the normal smooth curve) that the tibialis posterior tendon makes as it extends from the medial malleolus. This abnormality causes a focal point of friction at the medial malleolus (open arrow).

Media file 51: Ankle, tibialis posterior tendon injuries. Same patient as in Image 50 in Multimedia; axial intermediate-weighted MRI in a young adult at risk for tibialis posterior tendon dysfunction shows the accessory navicular with low-signal-intensity synchondrosis (open arrow).

Media file 52: Ankle, tibialis posterior tendon injuries. T2-weighted fat-suppressed MRI of the ankle in an adult woman with several months' history of medial ankle pain and tibialis posterior tendinopathy that is associated with subtendinous bone marrow edema of the medial malleolus. Axial image shows thickening of the tibialis posterior tendon (arrow). Note the marrow edema immediately subjacent to the medial malleolus (open arrow).

Media file 53: Ankle, tibialis posterior tendon injuries. Same patient as in Image 52 in Multimedia; T2-weighted fat-suppressed fast MRI of the ankle. Sagittal image shows thickening of the tibialis posterior tendon with increased internal signal intensity (arrow). Note the marrow edema immediately subjacent to the medial malleolus (open arrow).

Media file 54: Ankle, tibialis posterior tendon injuries. Axial T2-weighted MRI in an adult man with accessory navicular pseudoarthrosis. Image reveals fluid between the navicular and accessory navicular; this is consistent with pseudoarthritis. Also note the edema in both bones (open arrows); this reflects altered mechanics.

Media file 55: Ankle, tibialis posterior tendon injuries. Longitudinal sonogram in a young healthy woman shows a normal tibialis posterior tendon (between calipers). Arrow points to the medial malleolus.

Media file 56: Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Images 9 and 55; transverse sonogram in a young healthy woman shows a normal tibialis posterior tendon (between calipers). Open arrow points to the flexor digitorum longus tendon adjacent to tibialis posterior tendon.

Media file 57: Ankle, tibialis posterior tendon injuries. Same patient as in Multimedia Image 58; transverse color Doppler sonogram of tibialis posterior tendon in a young adult with tendinosis and peritendinosis. Image shows peritendinous (open arrow) and intratendinous (arrowheads) flow.

Media file 58: Ankle, tibialis posterior tendon injuries. Same patient as in Image 39 in Multimedia; transverse sonogram in a middle-aged woman with tendinosis shows an enlarged inhomogeneous tibialis posterior tendon (between calipers).

Media file 59: Ankle, tibialis posterior tendon injuries. Transverse sonogram in a young adult woman with peritendinosis (open arrow points to low echogenicity in peritendinous area).

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Keywords

tibialis posterior tendon Injury, tibialis posterior tendon dysfunction, ankle injury, tendinitis, tendonitis, tendonosis

Contributor Information and Disclosures

Author

Sherif Wassef, MD, MS, FRCS, Consulting Staff, Department of Vascular and Interventional Radiology, Hahnemann University Hospital
Sherif Wassef, MD, MS, FRCS is a member of the following medical societies: American College of Radiology, Royal College of Surgeons of Edinburgh, and Society of Interventional Radiology
Disclosure: Nothing to disclose.

Coauthor(s)

Maha Mikhail, MD, MS, FACC, Consulting Staff, Connecticut Multispecialty Group
Maha Mikhail, MD, MS, FACC is a member of the following medical societies: American College of Cardiology, American College of Physicians, and European Society of Cardiology
Disclosure: Nothing to disclose.

Medical Editor

Amilcare Gentili, MD, Professor of Clinical Radiology, University of California at San Diego; Consulting Staff, Department of Radiology, Thornton Hospital; Chief of Radiology, San Diego VA Health Care System
Amilcare Gentili, MD is a member of the following medical societies: American Roentgen Ray Society, Radiological Society of North America, and Society of Skeletal Radiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Thomas Lee Pope Jr, MD, FACR, Professor of Radiology and Orthopedics, Department of Radiology, Medical University of South Carolina
Thomas Lee Pope Jr, MD, FACR is a member of the following medical societies: American Roentgen Ray Society, International Skeletal Society, Radiological Society of North America, Society of Breast Imaging, and South Carolina Medical Association
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington
Felix S Chew, MD, MBA, EdM is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

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