peroneals

The peroneals, also known as the fibularis muscles, comprise two primary muscles in the lateral compartment of the leg: peroneus longus and peroneus brevis. They primarily act to evert the foot and assist in plantarflexion, contributing to lateral ankle stability during gait.

Anatomy: Peroneus longus originates from the head and upper two-thirds of the fibula and its fascia; its tendon runs behind the lateral malleolus and under the foot to insert on the base of the first metatarsal and the medial cuneiform. Peroneus brevis originates from the distal two-thirds of the fibula; its tendon travels behind the lateral malleolus and inserts on the tuberosity of the fifth metatarsal.

Innervation and blood supply: Both muscles are innervated by the superficial fibular (peroneal) nerve. Blood supply is via perforating branches of the fibular (peroneal) artery and adjacent muscular branches.

Function: Primary actions are eversion of the foot and plantarflexion of the ankle. They oppose the invertors (such as the tibialis posterior) and help stabilize the foot during stance and push-off. The longus also supports the transverse and medial arches through its medial-foot insertions.

Clinical significance: Peroneal tendons can be involved in injuries such as tendinopathy, tenosynovitis, or tears, especially after inversion injuries. Subluxation of the peroneal tendons can occur with retinacular injury. Injury to the superficial fibular nerve can reduce eversion and, in severe cases, cause foot drop.