The peroneus longus takes a remarkable path from the lateral fibula all the way across the sole of the foot to attach at the medial cuneiform and first metatarsal base, making it one of the few muscles in the body whose tendon travels in two completely different planes. Its long oblique course allows it to simultaneously evert the foot and depress the first metatarsal head, an action critical for stabilising the medial forefoot during push-off.
| Origin | Upper two-thirds of the lateral surface of the fibula and the head of the fibula |
|---|---|
| Insertion | Plantar surface of the medial cuneiform and the base of the first metatarsal, after crossing the sole of the foot in the cuboid tunnel |
| Nerve Supply | Superficial peroneal nerve (L4, L5, S1) |
| Blood Supply | Fibular artery |
| Actions | Eversion of the foot; Plantarflexion of the ankle; Stabilises the medial longitudinal arch from below by plantar-flexing the first ray |
|---|
By pulling the first metatarsal plantarward and the hindfoot into eversion it provides a windlass mechanism assist during push-off and dynamically stabilises the transverse arch from below, a role that makes it complementary to the tibialis anterior which pulls the medial foot upward.
The peroneus longus tendon passes through the cuboid tunnel on the lateral plantar foot, where it can be compressed or avulsed during lateral ankle sprains. Isolated peroneus longus tears or avulsions at the cuboid can cause persistent lateral ankle and plantar foot pain that is easily overlooked on standard ankle radiographs. Peroneus longus tendinopathy at the lateral malleolus is also a common overuse injury in runners with cavus foot alignment.
The peroneus longus is palpable on the lateral lower leg from the fibular head downward, and its tendon can be felt posterior to the lateral malleolus during resisted foot eversion. The tendon can occasionally be palpated within the cuboid tunnel on the plantar lateral foot.
Degenerative overuse at the lateral malleolus or cuboid tunnel producing lateral ankle and plantar foot pain that worsens with running and propulsive activities, especially in cavus foot types.
Avulsion of the tendon at its cuboid tunnel attachment during a lateral ankle sprain, producing persistent lateral plantar foot pain after the sprain symptoms resolve, confirmed by MRI or CT.
