Absence of plantarflexion during the Thompson test indicates?

• A. Achilles tendon continuity
• B. Posterior tibial tendon rupture
• C. Achilles tendon rupture
• D. Deltoid ligament injury

Answer: (C)

The test is checking the integrity of the Achilles tendon. When you squeeze the calf, the gastrocnemius–soleus complex contracts and should pull on the heel through the Achilles tendon, producing plantarflexion of the foot. If there is an Achilles tendon rupture, that connection is lost, so the foot fails to plantarflex. That absence of plantarflexion after squeezing the calf is therefore a sign of Achilles tendon rupture.

If the Achilles tendon were intact, plantarflexion would occur normally. The other options involve different structures: a posterior tibial tendon problem or a deltoid ligament injury would not produce a failure of plantarflexion on this test, though they could cause other signs of ankle dysfunction.