The fibularis longus everts and plantarflexes the foot.
In addition, the fibularis longus, tibialis anterior, and tibialis posterior muscles, which all insert on the undersurfaces of bones on the medial side of the foot, together act as a stirrup to support the arches of the foot. The fibularis longus supports mainly the lateral and transverse arches.
The fibularis longus is innervated by the superficial fibular nerve.