In human anatomy, the peroneus longus (also known as fibularis longus) is a superficial muscle in the lateral compartment of the leg, and acts to evert and plantarflex the ankle. The muscle, the longest and most superficial of the three peroneus muscles , is attached proximally to the head of the fibula and its ‘belly’ runs down most of this bone.
Peroneus (fibularis) longus muscle. The lateral compartment of the leg contains two fibular, or peroneal muscles. The function of this compartment is to protect the underlying neurovasculature, as well as allow the foot to evert and the ankle to plantarflex.
The muscle is considered an extrinsic ankle muscle; it originates in your leg and attaches to your foot and serves to move your ankle. The peroneus longus tendons are held in place near your lateral ankle by the superior peroneal retinaculum, a thick band of tissue. Peroneus longus is a superficial muscle that can easily be seen and palpated.