What is the classic clinical sign of Achilles tendon rupture?

• A. Pain with resisted plantarflexion only
• B. Inability to dorsiflex the foot
• C. Inability to plantarflex the foot
• D. Sensory loss over the heel

Answer: (C)

The hallmark of an Achilles tendon rupture is loss of plantarflexion strength. The Achilles tendon connects the gastrocnemius-soleus complex to the heel, so when it ruptures you can’t push the foot down against resistance. A classic confirmatory sign is the positive Thompson test: squeezing the calf fails to produce plantarflexion.

Dorsiflexion is controlled by muscles higher up the leg (and the nerves that innervate them), so an Achilles rupture doesn’t typically cause inability to dorsiflex. Sensory loss over the heel would imply a nerve injury, not an isolated tendon rupture. Pain with resisted plantarflexion can occur, but the defining feature is the complete inability to plantarflex.