The peroneus brevis is the shorter and deeper of the two peroneal muscles, running from the lower lateral fibula to the fifth metatarsal base in a straighter course than the peroneus longus. Its distal attachment at the prominent fifth metatarsal styloid makes it the tendon involved in the most common avulsion fracture in the ankle, and its split tears within the retromalleolar groove are among the most underdiagnosed sources of chronic lateral ankle pain.
| Origin | Lower two-thirds of the lateral fibular surface |
|---|---|
| Insertion | Styloid process at the base of the fifth metatarsal |
| Nerve Supply | Superficial peroneal nerve (L5, S1) |
| Blood Supply | Fibular artery |
| Actions | Eversion of the foot; Weak plantarflexion of the ankle |
|---|
As the primary evertor of the foot it resists inversion during lateral ankle sprains and is the first line of dynamic defence against ankle instability, which explains why it is frequently torn during the same mechanism that sprains the lateral ankle ligaments.
Peroneus brevis tendon split tears occurring within the retromalleolar groove behind the lateral malleolus are found in 10 to 37 percent of cadaver specimens, and are a significant cause of chronic posterolateral ankle pain that fails to resolve after standard lateral ankle sprain rehabilitation. The diagnosis is best made with MRI or ultrasound. The fifth metatarsal avulsion fracture at the brevis insertion is the most common fracture of the lateral foot and must be distinguished from the more serious Jones fracture at the metaphyseal-diaphyseal junction.
The peroneus brevis tendon is palpable as the anterior of the two peroneal tendons posterior to the lateral malleolus, and its insertion at the fifth metatarsal styloid is a bony landmark felt at the lateral foot just distal to the malleolus.
Longitudinal tearing of the tendon within the retromalleolar groove from chronic impingement or an acute ankle sprain, producing persistent posterolateral ankle pain that fails to resolve after standard sprain rehabilitation.
Avulsion of the peroneus brevis insertion at the styloid process during forced inversion, producing lateral foot pain at the base of the fifth metatarsal, distinguished from a Jones fracture by its location at the styloid rather than the metaphyseal-diaphyseal junction.
