Which sign is used to detect posterior tibial nerve entrapment at the ankle?

• A. Thompsons test
• B. Morton's test
• C. Tinel's sign (ankle)
• D. Bump test

Answer: (C)

Tinel's sign at the ankle is used to detect posterior tibial nerve entrapment at the tarsal tunnel. By tapping over the nerve as it passes behind the medial malleolus, reproduction of paresthesias in the plantar aspect of the foot indicates irritation or compression of the nerve within the tunnel. This sign specifically tests the nerve’s sensitivity in its course through the tarsal tunnel, which is what happens in posterior tibial nerve entrapment. The other signs assess different structures—Thompson’s test checks the Achilles tendon, Morton's test looks for interdigital nerve issues in the forefoot, and the bump test screens for fracture or contusion—so they don’t target the posterior tibial nerve entrapment in the ankle.