Peroneus Longus (also known as fibularis longus) is a superficial muscle in the lateral compartment of the leg, and acts to evert and plantarflex the ankle.
The muscle, the longest and most superficial of the three peroneus muscles, is attached proximally to the head of the fibula and its ‘belly’ runs down most of this bone. It becomes a tendon that goes posteriorly around the lateral malleolus of the ankle, then continues under the foot to attach to the medial cuneiform and first metatarsal. It is innervated by the Superficial peroneal nerve (L5,S1)
Anatomy of Peroneus Longus
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The peroneus longus is one of the three muscles that span the lateral leg – peroneus may also be interchanged with fibular, referring to the lateral bone of the lower leg running deep to the peroneal muscles
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Origin: The peroneus longus muscle originates on the head of the fibula and the upper half of the fibular shaft – this muscle crosses the ankle joint and courses deep into the foot and passes into a groove of the cuboid bone.
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Insertion: the posterolateral aspect of the medial cuneiform bone and the lateral portion of the base of the first metatarsal
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Action: The peroneus longus acts to evert the foot, plantarflex the ankle and adds support to the transverse arch of the foot
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Blood Supply: Anterior tibial artery
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Innervation: Superficial peroneal nerve
The fibularis longus muscle originates at the head and superior two-third of the lateral shaft of the fibula and the adjacent surface of intermuscular septa. It inserts at the plantar side of the medial cuneiform and first metatarsal bone.
Peroneus longus and brevis plantarflex the foot, while the peroneus tertius dorsiflexes it.
| Name | Compartment | Action | Nerve | Artery |
| Peroneus longus | lateral compartment | eversion and plantarflexion | superficial fibular nerve | fibular artery |
| Peroneus brevis | lateral compartment | eversion and plantarflexion | superficial fibular nerve | fibular artery |
| Peroneus tertius | anterior compartment | eversion and dorsiflexion | deep fibular nerve | anterior tibial artery |
The Function of Peroneus Longus
The peroneus longus and brevis muscles plantarflex the foot, in conjunction with the tibialis posterior, antagonizing the tibialis anterior and peroneus tertius, which are dorsiflexion of the foot.[rx]
- The peroneus longus also everts the sole of the foot, and from the oblique direction of the tendon across the sole of the foot is an important agent in the maintenance of the transverse arch.[rx]
- Taking their fixed points below, the peroneus muscles serve to steady the leg upon the foot.[rx]
- This is especially the case in standing upon one leg, when the tendency of the superincumbent weight is to throw the leg medialward; the peroneus longus overcomes this tendency by drawing on the lateral side of the leg.[rx]
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Functionally, the lateral compartment of the leg causes eversion and plantarflexion of the ankle. Recall that the talocrural joint allows for flexion and extension only, and inversion and eversion in fact occur at the subtalar joint. Muscles that cause inversion include tibialis anterior, and tibialis posterior. The lateral compartment muscles work with tibialis posterior (which is also a plantarflexor) to oppose the actions of the dorsiflexor muscles (tibialis anterior and fibularis tertius).
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