(See also Overview of Foot and Ankle Disorders.)
At the level of the ankle, the posterior tibial nerve passes through a fibro-osseous canal and divides into the medial and lateral plantar nerves. Tarsal tunnel syndrome refers to compression of the nerve within this canal, but the term has been loosely applied to neuralgia of the posterior tibial nerve resulting from any cause. Synovitis of the flexor tendons of the ankle caused by abnormal foot function, inflammatory arthritis (eg, rheumatoid arthritis), fibrosis, ganglionic cysts, fracture, and ankle venous stasis edema are contributing factors. Patients with hypothyroidism may develop tarsal tunnel–like symptoms as a result of perineural mucin deposition.
Pain (occasionally burning and tingling) is usually retromalleolar and sometimes in the plantar medial heel and may extend along the plantar surface as far as the toes. Although the pain is worse during standing and walking, pain at rest may occur as the disorder progresses, which helps to distinguish it from plantar fasciosis.
Tapping or palpating the posterior tibial nerve below the medial malleolus at a site of compression or injury often causes distal tingling (Tinel sign). Although false-negative results on electrodiagnostic tests are somewhat common, a positive history combined with supportive physical findings and positive electrodiagnostic results makes the diagnosis of tarsal tunnel syndrome highly likely. Plantar heel and arch pain lasting > 6 months also strongly suggests distal tibial plantar nerve compression with entrapment. The cause of any swelling near the nerve should be determined.
Strapping the foot in a neutral or slightly inverted position and elevating the heel or wearing a brace or orthotic that keeps the foot inverted reduces nerve tension. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be used initially and may relieve some symptoms. Local infiltration of an insoluble corticosteroid/anesthetic mixture may be effective if the cause is inflammation or fibrosis. Surgical decompression may be necessary to relieve suspected fibro-osseus compression with recalcitrant symptoms.