Anatomy OIAN Practice Test

Inversion of the foot (sole turning inward) combined with plantarflexion (pointing the foot downward) is best produced by the tibialis posterior. This muscle lies in the deep posterior compartment and its tendon travels behind the medial malleolus to insert on the navicular and other midfoot tarsals. When it contracts, it pulls the hindfoot and midfoot into inversion while assisting with plantarflexion at the ankle, and it also helps support the medial arch for stability during gait.

Tibialis anterior mainly dorsiflexes the foot and can invert, but its primary action is lifting the foot upward rather than pushing it downward. Extensor digitorum longus extends the toes and dorsiflexes and everts, not inversion paired with plantarflexion. Flexor hallucis longus plantarflexes the foot and inverts, but its main role is flexing the big toe, not serving as the principal inverter with plantarflexion.