Fibularis longus muscle

At a glance

English

Fibularis longus muscle

Latin (TA2)

Musculus fibularis longus

System

Muscle

Region

Lower limb

Side

Paired, left and right

About the fibularis longus muscle

Fibularis longus, or peroneus longus, is the longer and more superficial of the pair that fill the leg's lateral compartment. Its belly runs down the outer side of the fibula, over fibularis brevis, and its tendon takes an unusual course: behind the ankle, around the outer edge of the foot and right across the sole to its inner side.

It arises from the fibular head and from the bone's outer face over its upper two-thirds, from the deep fascia, and from the septa it shares with the front and back compartments; a few fibres may come from the lateral tibial condyle. Between its attachments to the fibular head and shaft is a gap where the common fibular nerve winds forwards around the neck of the fibula, a spot where the nerve is easily pressed or injured.

The tendon runs behind the lateral malleolus, behind the brevis tendon, in a groove closed by the superior fibular retinaculum. It passes forwards below the fibular trochlea of the calcaneus under the inferior retinaculum, then turns into the sole in a groove on the cuboid, bridged by the long plantar ligament. It crosses the sole obliquely and ends on the outer sides of the first metatarsal base and the medial cuneiform. Where it bends around the cuboid it thickens, and a small sesamoid, the os peroneum, often forms there.

The muscle everts the foot and plantarflexes the ankle, opposing tibialis anterior. Because its tendon slings under the foot from outside to inside, it pulls the first metatarsal down, helps hold the transverse and lateral arches, and presses the big-toe side of the forefoot to the ground during push-off. Working from below, it steadies the leg on the foot when standing on one leg. Its nerve is the superficial fibular nerve, which arises from the common fibular nerve in the gap at the top of the muscle.

Attachments, action and supply

Origin

Fibular head and the outer face of the fibula over its upper two-thirds, deep fascia and intermuscular septa; sometimes the lateral tibial condyle.

Insertion

Outer sides of the first metatarsal base and the medial cuneiform.

Action

Everts the foot and plantarflexes the ankle; supports the transverse and lateral arches and steadies the leg on the foot.

Nerve supply

Superficial fibular nerve (L5, S1, S2).

Blood supply

Branches of the anterior tibial and fibular arteries.