Tarsal Tunnel Syndrome: Nerve Compression at the Inner Ankle

The Tarsal Tunnel

The tarsal tunnel is a fibro-osseous canal on the medial (inner) aspect of the ankle, formed by the medial malleolus and calcaneus on one side and the flexor retinaculum — a fibrous band of connective tissue — on the other. Through this tunnel pass the structures supplying the heel and sole of the foot: the posterior tibial artery and veins, and the tibial nerve with its three branches — the medial plantar nerve, the lateral plantar nerve, and the medial calcaneal nerve. The tibial nerve divides into these branches within or just distal to the tunnel. Any increase in pressure within the tunnel — from swelling, a space-occupying lesion, or structural deformity — compresses the nerve and its branches, producing the symptom complex of tarsal tunnel syndrome.

Causes and Contributing Factors

Tarsal tunnel syndrome has both intrinsic and extrinsic causes. Intrinsic causes include varicose veins within the tunnel (common and frequently overlooked), ganglion cysts, lipomas, posterior tibial tendon tenosynovitis, and accessory muscles. Extrinsic causes include excessive foot pronation (which stretches the tibial nerve and reduces tunnel volume), post-traumatic scar tissue following ankle fracture or sprain, and space-occupying conditions such as inflammatory arthropathy or oedema. Unlike carpal tunnel syndrome, tarsal tunnel syndrome does not have a clearly dominant identifiable cause — in many cases it is multifactorial, and identifying and addressing all contributing factors is necessary for successful management.

Symptoms and Diagnosis

The classic presentation is burning, tingling, or numbness on the sole of the foot, often extending from the heel to the toes. Symptoms are typically worse with prolonged standing and walking, at night, and with activities that increase pronation. Unlike plantar fasciitis, the pain is characteristically neuralgic in quality — burning and electric rather than aching — and may be accompanied by a feeling that the foot is "swollen" even when it is not. Tinel's sign — tapping over the tibial nerve posterior to the medial malleolus to reproduce tingling in the sole — is the primary clinical test, though its sensitivity is variable. Electrodiagnostic studies (nerve conduction velocity and electromyography) confirm delayed tibial nerve conduction and help exclude proximal nerve pathology. Ultrasound and MRI can identify space-occupying lesions within the tunnel.

Management

Conservative management is the appropriate first approach. Orthotic support to control excessive pronation reduces tibial nerve stretch and tunnel pressure — a custom or prefabricated medial arch support addresses the mechanical loading component. Activity modification — reducing prolonged standing and avoiding aggravating footwear — is important in the acute phase. Manual therapy to the tarsal tunnel region, tibial nerve neurodynamic mobilisation, and soft tissue work to the flexor retinaculum and plantar fascia can improve nerve gliding and reduce intraneural sensitisation. Corticosteroid injection into the tarsal tunnel provides meaningful pain relief for inflammatory contributors. Surgical decompression (release of the flexor retinaculum) is considered when a space-occupying lesion is identified, or when extended conservative management has failed — outcomes are most favourable when a clear structural cause has been identified preoperatively.