The fibularis longus, also referred to as the peroneus longus, is a muscle inside the lateral area of the human leg, which everts and flexes the ankle. Of the three muscles in the peroneus group in the lateral area of the leg, it is the most superficially situated. The other two muscles in the peroneous group are the peroneus brevis and peroneus tertius. Attached to the head of a fibula, it is controlled by the fibular nerve. Blood flow is provided to the peroneus longus by the fibular artery. It runs the length of the fibula and turns into a tendon at the lateral malleolus attached to the ankle. It stretches to the underside of the foot and attaches to the first metarsal and the medial cuneiform. The fibularis longus works in conjunction with the tendons of the peroneal retinaculum to help to steady a leg upon a foot, especially when the person is standing on one leg, when plantarflexion is especially important.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Fibularis longus