The peroneus longus primarily facilitates which movement of the foot?

• A. Eversion of the foot
• B. Inversion of the foot
• C. Dorsiflexion of the ankle
• D. Plantarflexion of the ankle

Answer: (A)

The key idea is understanding what the peroneus longus does in the foot. This muscle sits on the lateral side of the leg and its tendon crosses behind the outer ankle and under the foot to attach on the plantar surface of the medial foot. When it contracts, it pulls the lateral side of the foot upward and the sole tilts outward, producing eversion. That is its primary action. It can assist with plantarflexion, but the main role is eversion. In contrast, inversion is mainly done by tibialis muscles, dorsiflexion by the muscles on the front of the leg, and plantarflexion by the calf muscles, so those movements aren’t the primary actions of the peroneus longus.