Peroneus Brevis

Origin, Insertion, Action, Innervation

Origin: Distal two-thirds of the lateral surface of the fibula and the adjacent intermuscular septa
Insertion: Tuberosity at the base of the fifth metatarsal (lateral foot)
Action:
Primary: Eversion of the foot
Plantarflexion of the ankle (assists)
Dynamic lateral ankle stabilization during gait
Innervation: Superficial peroneal (fibular) nerve (L5, S1)

Palpation Guide

Client position: Sidelying with the lateral leg up, or supine with the leg in slight external rotation.
Landmark sequence:

Locate the lateral malleolus. The peroneus brevis tendon passes directly posterior to it, deep to (and slightly anterior to) the peroneus longus tendon.
Follow the tendon distally from behind the lateral malleolus along the lateral foot to the base of the fifth metatarsal — the prominent bony bump on the lateral midfoot that is easy to find.
The muscle belly lies on the distal two-thirds of the fibula, deep to peroneus longus proximally. In the distal lateral leg, brevis becomes more accessible as longus transitions to tendon.

Tissue feel: The tendon behind the lateral malleolus lies deep to longus and is slightly flatter. At the fifth metatarsal base insertion, it is cordlike and readily palpable. The muscle belly feels similar to longus but is smaller and deeper.
Confirmation test: Ask the client to evert the foot against resistance. Palpate the tendon at the fifth metatarsal base — it tightens distinctly. To differentiate from longus, note that brevis pulls the lateral foot directly outward (pure eversion), while longus also plantarflexes the first ray.
Common errors:
Confusing the fifth metatarsal tuberosity with a fracture — the normal tuberosity (brevis insertion) is prominent and can be tender. Acute tenderness with a history of ankle inversion and inability to bear weight suggests an avulsion fracture (the tendon pulls a bone chip off the base during forced inversion). This requires imaging.

Trigger Point Referral

Common TrP locations: In the distal muscle belly on the lateral fibular surface, approximately in the lower third of the leg.
Referral pattern: Pain over and below the lateral malleolus, extending to the lateral heel.
Clinical significance: Referral to the lateral heel overlaps with calcaneal (heel) pathology and lateral ankle sprain pain. Persistent lateral ankle "soreness" months after a sprain may be peroneus brevis TrPs maintaining the pain pattern after the ligament has healed.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Peroneus Brevis at TriggerPoints.net](http://www.triggerpoints.net/muscle/peroneus-brevis).

Clinical Notes

Common conditions:

Peroneus brevis tendon split (longitudinal tear) is the most common peroneal tendon injury. The tendon is compressed between the fibula and peroneus longus tendon as it wraps the malleolus, making it susceptible to mechanical damage during inversion sprains or chronic subluxation.
Fifth metatarsal avulsion fracture ("dancer's fracture") — during a forceful ankle inversion, peroneus brevis can avulse a fragment from the fifth metatarsal base. Acute tenderness at the fifth metatarsal base after an inversion injury should be assumed to be a fracture until imaging rules it out.
Frequently involved in chronic lateral ankle instability — the peroneals compensate for deficient lateral ligaments, and peroneus brevis bears the primary dynamic stabilizing role.

What you'll typically find:

In clients with a history of recurrent ankle sprains, peroneus brevis is often chronically overloaded and tender along its tendon behind the lateral malleolus. The muscle has been working overtime to compensate for lateral ligament laxity.
Tenderness at the fifth metatarsal base is common in clients who wear rigid or narrow footwear — the insertion is compressed against shoe material during eversion.
In peroneal tendon subluxation, the client may report a visible or palpable "popping" behind the lateral malleolus during active eversion. The brevis tendon is typically the one that displaces.

Treatment effects:

Cross-fiber friction on the tendon behind the lateral malleolus is effective for tendinopathy. Position the foot in slight inversion to expose the tendon.
Longitudinal stripping of the muscle belly along the distal fibular surface addresses the distal TrP effectively.
The fifth metatarsal insertion responds to localized friction for insertional tendinopathy, but palpate carefully — if there is a recent inversion injury, rule out avulsion fracture before applying friction.

Cautions:

The same nerve proximity cautions as peroneus longus apply — the superficial peroneal nerve runs in the lateral compartment and can be compressed by deep work in the distal leg.
Acute tenderness at the fifth metatarsal base after an inversion injury requires imaging before treatment. An avulsion fracture at this site is common and easily missed clinically.

Clinical pearl:

The peroneal tendons are retained behind the lateral malleolus by the superior peroneal retinaculum. When this retinaculum tears (usually in an inversion sprain), the tendons sublux forward over the malleolus. If you can reproduce the subluxation on examination, the retinaculum is torn — this often requires surgical repair if the client is active. Do not aggressively massage tendons that are subluxing; stabilization is the priority.

Assessment

Resisted eversion:

Same test as for peroneus longus — both peroneals contract together. Pain specifically at the fifth metatarsal base or behind the lateral malleolus localizes to peroneus brevis.

Fifth metatarsal palpation:

Direct palpation of the fifth metatarsal tuberosity. Tenderness here after an inversion injury raises suspicion for avulsion fracture. If the client cannot bear weight on the lateral forefoot, refer for imaging.

Peroneal tendon integrity:

Client seated. Ask for repeated active eversion while you palpate behind the lateral malleolus. A palpable "clunk" or visible displacement of the tendon indicates subluxation.

Muscle Groups

Lateral compartment (anatomical):

Peroneus longus
Peroneus brevis (this article)

Foot evertors (functional):

Peroneus longus
Peroneus brevis (this article)
Extensor digitorum longus (assists)

Superficial peroneal nerve group (innervation):

Peroneus longus
Peroneus brevis (this article)

Related Muscles

Synergists for eversion:

Peroneus longus — lateral compartment partner with longer tendon and plantar crossing

Antagonists (inversion):

Tibialis anterior — primary inverter and dorsiflexor
Tibialis posterior — primary inverter and plantarflexor

Key Takeaways

Most commonly injured peroneal tendon — vulnerable to longitudinal splitting behind the lateral malleolus.
Fifth metatarsal base tenderness after an inversion injury may indicate avulsion fracture — refer for imaging before treating.
Primary dynamic lateral ankle stabilizer alongside peroneus longus — must be strengthened after ankle sprains.