Tarsal tunnel syndrome is a condition analogous to carpal tunnel syndrome, with the former condition affecting the foot and the latter affecting the wrist. 
The tarsal tunnel is bounded by the ankle bone on one side and a band of fibrous tissue, called the flexor retinaculum, on the other. The main nerve serving the foot, the posterior tibial nerve, runs through this tube, or tunnel. Tarsal tunnel syndrome is caused by compression of this nerve, which in turn causes the nerve to become inflamed and stop working properly.
Tarsal tunnel syndrome is one of several conditions that can cause heel pain, numbness, and tingling. It can also cause pain on the underside (plantar surface) of the sole and toes.