Which muscles contribute to ankle eversion?

• A. Peroneus longus, Peroneus brevis, & Peroneus tertius
• B. Tibialis posterior
• C. Gastrocnemius
• D. Flexor hallucis longus

Answer: (A)

Ankle eversion is produced by muscles that pull the sole of the foot outward, away from the midline. The primary evertors are the peroneal muscles in the lateral compartment of the lower leg: peroneus longus, peroneus brevis, and peroneus tertius. They attach from the fibula to the foot and direct the rear and midfoot outward, with peroneus tertius also aiding in dorsiflexion. Because of their location and line of pull, these muscles are the main contributors to eversion.

The other muscles listed do not primarily cause eversion. Tibialis posterior and flexor hallucis longus mainly invert the foot, pulling the sole toward the midline. Gastrocnemius mainly plantarflexes the ankle (and assists with knee flexion) rather than everting. So the trio of peroneal muscles best explains ankle eversion.