Fibularis Brevis (Peroneus)
Leg · Lower Limb
The fibularis brevis (peroneus brevis) is the shorter and deeper of the two muscles of the lateral compartment of the leg, lying beneath the fibularis longus. It arises from the lower two-thirds of the lateral surface of the fibula, and its tendon passes behind the lateral malleolus to insert on the tuberosity of the fifth metatarsal. Working with the fibularis longus, it everts the foot and assists plantarflexion of the ankle. It is supplied by the superficial fibular (peroneal) nerve (L5, S1, S2). Because its tendon anchors to the base of the fifth metatarsal, forceful inversion can avulse a fragment of bone at that site.
Origin, Insertion, Action & Nerve
Origin
Lower two-thirds of lateral surface of fibula
Insertion
Tuberosity of 5th metatarsal
Action
Eversion of foot; plantarflexion of ankle
Nerve
Superficial fibular (peroneal) nerve (L5, S1, S2)
Attachments explained
The Fibularis Brevis (Peroneus) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Lower two-thirds of lateral surface of fibula
Insertion
Tuberosity of 5th metatarsal
Action & function
When the Fibularis Brevis (Peroneus) contracts, it produces the following movements: Eversion of foot; plantarflexion of ankle.
As part of the Leg group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Fibularis Brevis (Peroneus) receives its nerve supply from the Superficial fibular (peroneal) nerve (L5, S1, S2). This nerve carries fibres from spinal segment(s) L5, S1, S2.
Because a muscle can only contract when its nerve is intact, injury to the Superficial fibular or to its spinal roots (L5, S1, S2) can weaken or paralyse the Fibularis Brevis (Peroneus), impairing the movements it normally produces (eversion of foot). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Fibularis Brevis (Peroneus) (the OIANS method)
Learn the fibularis brevis as the everter with the short, direct route: unlike its long partner, its tendon stops at the tuberosity of the fifth metatarsal on the lateral border of the foot, which you can palpate as a bony prominence midway along the outer edge. Reasoning from this lateral insertion behind the lateral malleolus explains both eversion and its assist to plantarflexion.
Anchor the muscle with a clinical hook: because it pulls on the base of the fifth metatarsal, a sudden inversion injury can tear off a fragment of that bone, the classic avulsion fracture that mimics an ankle sprain. Keep it paired with fibularis longus under the shared superficial fibular nerve (L5, S1, S2), remembering that longus goes medial across the sole and brevis stays lateral.
Frequently asked questions
Where is the Fibularis Brevis (Peroneus) located?
The Fibularis Brevis (Peroneus) is a muscle of the Leg group, located in the Lower Limb.
What is the origin of the Fibularis Brevis (Peroneus)?
Lower two-thirds of lateral surface of fibula
What is the insertion of the Fibularis Brevis (Peroneus)?
Tuberosity of 5th metatarsal
What movements does the Fibularis Brevis (Peroneus) produce?
Eversion of foot; plantarflexion of ankle
What nerve supplies the Fibularis Brevis (Peroneus)?
Superficial fibular (peroneal) nerve (L5, S1, S2)
Is the Fibularis Brevis (Peroneus) free to study in OIANS?
The Fibularis Brevis (Peroneus) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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