Tarsal Tunnel Tarsal tunnel syndrome is a compressive neuropathy of the posterior tibial nerve as it passes through the tarsal tunnel on the medial side of the ankle. This tunnel is bordered by the flexor retinaculum, the calcaneus, and the medial malleolus, with several structures—including the posterior tibial tendon, flexor digitorum longus, and flexor hallucis longus—running alongside the nerve. When the nerve becomes irritated or compressed within this space, it can produce symptoms such as