Peroneal Strain

Anatomy

There are generally two peroneal muscles—the peroneus longus and peroneus brevis—that originate on the outside (lateral) part of the lower leg. A small percentage of the population has an additional or accessory peroneus muscle, the peroneus quartis. The peroneus longus begins high on the fibula, while the peroneus brevis originates from the lower two thirds of the fibula. At the end of the [Page 1072]muscle, just before the lateral ankle bone (malleolus), the muscular part becomes tendon, and the two tendons come together in a sheath. As the tendons course around the ankle bone, they enter a fibro-osseous tunnel, which helps in holding them in place as they make this turn. This tunnel is called the retromalleolar groove and is covered by connective tissue called the superior retinaculum. This is the primary restraint keeping the tendons in place in the groove. Beyond the ankle, the tendons split from their sheath and tunnel, and the peroneus brevis inserts on the outside of the midfoot (tuberosity of the fifth metatarsal), while the peroneus longus travels along the undersurface (plantar surface) of the foot and inserts onto the first metatarsal.

Causes