Tarsal Tunnel Syndrome
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Tarsal tunnel syndrome occurs when there is compression neuropathy of the posterior tibial nerve as it passes behind the medial malleolus and under the flexor retinaculum (laciniate ligament) in the medial ankle (the tarsal tunnel).
- Women are slightly more affected than men (56%).
- All postpubescent ages are affected.
Etiology and Pathophysiology
- Contents within the tarsal tunnel from the anterior medial to the posterior lateral side include the following: the posterior tibial tendon, the flexor digitorum longus tendon, the posterior tibial artery and veins, the posterior tibial nerve, and the flexor hallucis tendon.
- The posterior tibial nerve passes through the tarsal tunnel, which is formed by three osseus structures—sustentaculum tali, medial calcaneus, and medial malleolus—covered by the laciniate ligament.
- Compression of the posterior tibial nerve within the tarsal tunnel results in decreased blood flow, ischemic damage, and resultant symptoms (1).
- Chronic compression can destroy endoneurial microvasculature, leading to edema and (eventually) fibrosis and demyelination (2).
- Increased pressure in the tarsal tunnel is caused by a variety of mechanical and biochemical mechanisms. The specific cause for compression is identifiable in only 60–80% of patients (1).
- Three general categories: trauma, space-occupying lesions, deformity (1)
- Trauma including displaced fractures, deltoid ligament sprains, or tenosynovitis
- Hindfoot varus or valgus
- Fibrosis of the perineurium
- Other causes:
- Osseous prominences
- Ganglia; lipoma; neurilemmoma
- Inflammatory synovitis
- Pigmented villonodular synovitis
- Tarsal coalition
- Accessory musculature
- In patients with systemic disease (e.g., diabetes), the “double crush” syndrome refers to the development of a second compression along the same nerve at a site of anatomic narrowing in patients with previous proximal nerve damage (3).
- Tarsal tunnel syndrome is associated with certain occupations and activities involving repetitive and prolonged weight-bearing on the foot and ankle (walking, running, dancing).
- Other possible risk factors include (4):
- Systemic inflammatory arthritis
- Connective tissue disorders
- Heel varus or valgus
- Bifurcation of the posterior tibial nerve into medial and lateral plantar nerves proximal to the tarsal tunnel