Peroneus Longus
| Pronuncation | |
| Derivation | |
| Origin | Lateral surface of the fibula, front of the head of the fibula, and the lateral condyle of the tibia. |
| Insertion | A tendon that runs down the posterior side of the ankle and under the foot to the first metatarsal. |
| Action | Points the foot, draws the bottom of the foot laterally. |
Peroneus longus forms a kind of central axis for the lower leg on the lateral side. Most of its belly lies on the upper third of the fibula. Its prominent tendon forms a straight line down the bone, and is especially visible a few inches above the ankle. (Below this point, the tendon runs deeply to the underside of the foot and cannot be seen.)
Because of its attachment on the first metatarsal, a strongly tensed peroneus longus will pull the big toe past the line of the other toes when rotating the sole of the foot laterally.
Orginating lower on the fibula is peroneus brevis, which appears on either side of the tendon of peroneus longus. This muscle assists the function of peroneus longus. When tensed, it is a second bulk in line with longus, with the tendon of longus coasting over the surface to the ankle.
The tendon of peroneus brevis can be seen moving forward and diagonally down the lateral side of the foot, wrapped around the underside of the ankle.
The lower leg in a lateral view could be divided into three columns: the calf mass in back, tibialis and its neighbors (the muscles discussed above) in front, and peroneus longus and brevis in the middle.