Which muscles are the prime movers for ankle plantarflexion?

Which muscles are the prime movers for ankle plantarflexion?

• A. Tibialis anterior
• B. Gastrocnemius, Soleus, & Plantaris
• C. Peroneus longus
• D. Flexor digitorum longus

Answer: (B)

Ankle pointing downward is driven mainly by the muscles in the back of the lower leg that attach to the heel via the Achilles tendon. The big players are the gastrocnemius and the soleus. Together they form the powerful plantarflexors, often called the triceps surae, and their combined pull bends the ankle downward. The gastrocnemius crosses both the knee and the ankle, so it contributes most when the knee is extended, while the soleus sits lower and provides strong plantarflexion regardless of knee position, making it the workhorse when the knee is bent. Plantaris is a small, thin muscle that also crosses the ankle and knee and can assist with plantarflexion, but its contribution is minor compared with the two main muscles. It’s often considered a supplementary part of the plantarflexor group. The other muscles listed don’t serve as primary plantarflexors: the tibialis anterior mainly dorsiflexes the ankle; the peroneus longus mainly everts the foot with some plantarflexion; and the flexor digitorum longus primarily flexes the toes and only assists indirectly with ankle plantarflexion.

Ankle pointing downward is driven mainly by the muscles in the back of the lower leg that attach to the heel via the Achilles tendon. The big players are the gastrocnemius and the soleus. Together they form the powerful plantarflexors, often called the triceps surae, and their combined pull bends the ankle downward. The gastrocnemius crosses both the knee and the ankle, so it contributes most when the knee is extended, while the soleus sits lower and provides strong plantarflexion regardless of knee position, making it the workhorse when the knee is bent.

Plantaris is a small, thin muscle that also crosses the ankle and knee and can assist with plantarflexion, but its contribution is minor compared with the two main muscles. It’s often considered a supplementary part of the plantarflexor group.

The other muscles listed don’t serve as primary plantarflexors: the tibialis anterior mainly dorsiflexes the ankle; the peroneus longus mainly everts the foot with some plantarflexion; and the flexor digitorum longus primarily flexes the toes and only assists indirectly with ankle plantarflexion.