Tarsal tunnel syndrome symptoms during running are most likely due to which condition?

• A. Low-lying muscle belly of the tibialis posterior
• B. Nerve entrapment at the deep peroneal nerve
• C. Plantar fasciitis
• D. Anterior talofibular ligament sprain

Answer: (A)

Dynamic compression of the posterior tibial nerve within the tarsal tunnel during running is the key idea. A low-lying tibialis posterior muscle belly can encroach on the nerve as the foot plantarflexes and inverts with activity, reducing the already tight space behind the medial malleolus. This extra bulk increases nerve irritation during running, producing the classic tarsal tunnel symptoms such as plantar foot numbness, burning, or paresthesias that worsen with activity.

Other conditions don’t fit the pattern as well. Entrapment of the deep peroneal nerve tends to produce dorsum-foot symptoms between the first web space and is not confined to the tarsal tunnel. Plantar fasciitis causes heel pain under the plantar fascia, especially with initial steps, not a neuropathic pattern. An anterior talofibular ligament sprain causes lateral ankle pain and instability from an ankle sprain, not tarsal tunnel-type neuropathy.