Entrapment of the distal branches of the posterior TIBIAL NERVE (which divides into the medial plantar, lateral plantar, and calcanial nerves) in the tarsal tunnel, which lies posterior to the internal malleolus and beneath the retinaculum of the flexor muscles of the foot. Symptoms include ankle pain radiating into the foot which tends to be aggravated by walking. Examination may reveal Tinel's sign (radiating pain following nerve percussion) over the tibial nerve at the ankle, weakness and atrophy of the small foot muscles, or loss of sensation in the foot. (From Foot Ankle 1990;11(1):47-52).