Which muscle primarily extends the ankle?

• A. Gracilis
• B. Gastrocnemius
• C. Soleus
• D. Tibialis Anterior

Answer: (C)

Extending the ankle means plantarflexion at the ankle joint. The main muscles that do this are the soleus and the gastrocnemius, together forming the calf group that pulls on the Achilles tendon to push the foot downward. The soleus stands out as the primary ankle extender because it crosses only the ankle joint, providing strong, steady plantarflexion especially during standing and low-intensity movements. It isn’t affected by knee position, so its contribution to ankle extension is reliable. The gastrocnemius also plantarflexes the ankle, but it crosses the knee as well, so its ability to extend the ankle depends on how bent the knee is; when the knee is flexed, its effectiveness decreases. It also has a knee-flexing role, which can obscure its function as an ankle extensor. The other muscles listed don’t plantarflex the ankle—tibialis anterior dorsiflexes the foot, and gracilis acts on the thigh. Hence, the soleus is the best answer for the primary ankle extensor.