Anatomy of the peroneal muscles (longus, brevus and tertius)
The Peroneal muscles are a group of muscles that originate from fibula (lower leg bone) and for this reason, these are also known as fibularis muscles. All these muscles insert into the bones of the mid foot called tarsals and metatarsals, which are present between bones of the ankle and the toes.
Both Peroneal longus and brevis muscles are present on the lateral side of the leg, while peroneal tertius is present on the anterior side.
Peroneal longus is present high on the lateral side of the leg. It is the most superficial of the three muscles. Peroneal brevis is also present on the lateral side of the leg, just inside the peroneal longus muscle. Brevis is much shorter and is attached at the fibula much lower than peroneal longus.
Both these muscles run on the lateral side of the leg; at the lower end these muscles convert into tendons, which run side by side, pass behind the outer bump of ankle.
The tendon of peroneal longus inserts into the first metatarsal (related to big toe) and that of the peroneal brevis inserts into the fifth metatarsal (related to fifth or smallest toe). Both tendons insert into the lower surface of these metatarsals.
Nerve and Blood supply
Both peroneal longus and brevis are supplied by superficial fibular nerve and artery. Peroneal tertius is supplied by deep fibular nerve and anterior tibial artery.
Both peroneal longus and brevis muscles bend the foot downward (plantarflexion) and twist it outward (eversion).
Peroneal tertius has a weak pull and lifts the foot upwards (dorsiflexion) and twists it outwards (eversion).
Thge peroneal muscles help to keep the legs steady upon the feet. The action of peroneal longus is especially significant when one is standing on a single leg. The lateral pull of this muscle prevents from falling towards the side of the raised leg.