Peroneal Tendinopathy

There are two peroneal muscles on the outside of the lower leg whose tendons run along the outside border of the foot with one inserting into the outside of the base of the 5th toe (peroneus brevis) and the second running under the foot and inserting into the base of the 1st metatarsal (peroneus longus). Most people have a third peroneal muscle the peroneus tertius which originates in a similar area but runs on to the top of the outside of the foot.

The role of these muscles is to evert the foot and ankle (roll in) and flex the ankle and foot (except peroneus tertius which weakly pulls the foot up). The peroneous longus also flexes the 1st metatarsal.

Problems can present in these tendons when they are overworked in certain foot postures, with ankle instability and they can become spastic causing a very flat foot appearance.

In stroke victims commonly these muscles can become very weak as nerves can no longer communicate with them and can be one factor in ‘foot drop’.