Tibialis posterior tendinosis, which is degeneration of the tibialis posterior tendon, and tibialis posterior tenosynovitis are the most common causes of pain behind the medial malleolus.
The posterior tibial tendon lies immediately behind the medial malleolus. Degeneration results from long-standing biomechanical problems, such as excessive pronation (often in people with obesity), hindfoot valgus or chronic tenosynovitis. A rearfoot tarsal coalition can create a rigid pes planus deformity and limit the function of the posterior tibialis tendon.
Tenosynovitis of the tendon sheath begins with acute inflammation. The tendon can be involved by primary inflammatory disorders, such as rheumatoid arthritis or gout.
(See also Overview of Foot and Ankle Disorders.)
Symptoms and Signs
Early on, patients experience occasional pain behind the medial malleolus. Over time, the pain becomes severe, with painful swelling behind the medial malleolus. Normal standing, walking, and standing on the toes become difficult. If the tendon ruptures (eg, with chronic tendinosis), the foot may acutely flatten (arch collapse) and pain may extend into the sole.
In cases of chronic tendinosis without rupture, the medial column (arch) height decreases gradually. The pull of the Achilles tendon is altered and creates a hindfoot valgus, which, in turn, contributes to degenerative changes at the subtalar joint and progression to arthritis. In late stages, the ankle joint will undergo arthritic changes due to the hindfoot valgus deformity.
In tenosynovitis, pain is typically more acute and the tendon may feel thick and swollen as it courses around the medial malleolus.
Diagnosis
Clinical evaluation
Radiographs
MRI
Tibialis posterior tendinosis and tenosynovitis are diagnosed clinically. Palpation of the tendon with the foot in an inverted plantar flexed position with applied resistance is usually painful. Standing on the toes is usually painful and may not be possible if the tendon is ruptured or severely dysfunctional. Pain and swelling with tenderness of the tibialis posterior tendon behind the medial malleolus is suggestive of tenosynovitis. Unilateral arch collapse with medial ankle bulging and forefoot abduction (too many toes sign) is particularly suggestive of advanced tendon pathology and warrants testing for tendon rupture.
Image courtesy of James C. Connors, DPM.
Radiographs may be performed to rule out other structural abnormalities contributing to medial ankle pain (eg, os naviculare, an accessory bone that can become symptomatic). In addition, advanced tendinopathy can result in a collapsed foot arch, which on radiograph shows loss of arch height and joint malalignment of the subtalar, talonavicular, naviculocuneiform, and/or the calcaneocuboid joints. The calcaneus inclination angle is lost and the talar declination angle is flattened. The subtalar joint is narrowed due to calcaneal eversion.
MRI or ultrasonography can confirm a fluid collection around the tendon (indicating tenosynovitis) or the extent of chronic degradation or tearing to the tendon with associated tendinosis.
Treatment
Orthotics and braces or surgery
Complete rupture of the tibialis posterior tendon requires surgery if normal function is the goal. Surgery is especially important in young active patients with acute tears.
Conservative therapy consists of mechanically off-loading the tendon by using orthotics modified with a deepened heel cup and appropriate medial wedging or posting in less severe pathology. Custom-molded ankle and foot bracing that extends the leg for added stability is indicated in more severe pathology.
Corticosteroid injections exacerbate the degenerative process (see Considerations for Using Corticosteroid Injections).
For tenosynovitis, rest and aggressive anti-inflammatory therapy are warranted.
