Overview

Share of body weight≈6–17%

The fibula has a head (with an apex/styloid process, attachment of the fibular collateral ligament and biceps femoris), which articulates with the lateral tibial condyle at the plane synovial proximal tibiofibular joint; a narrow neck, around which the common fibular (peroneal) nerve winds superficially; a long, thin, twisted shaft with an interosseous border for the interosseous membrane; and a distal lateral malleolus.

The lateral malleolus is longer and lies more distally (≈1 cm) and posteriorly than the medial malleolus. Its medial triangular facet articulates with the talus, forming the lateral wall of the ankle mortise; behind it, a groove carries the tendons of fibularis longus and brevis. Below and behind the articular facet, the malleolar fossa receives the posterior talofibular ligament. Distally the fibula is bound to the tibia by the distal tibiofibular syndesmosis (anterior and posterior inferior tibiofibular ligaments and interosseous ligament).

The fibula carries only ≈6–17% of body weight but is essential for ankle stability; it gives origin to the fibular muscles, the deep posterior compartment (tibialis posterior, flexor hallucis longus) and extensors.

Location: Lateral leg, from below the knee to the lateral ankle.

Parts & subdivisions

Head and apex
Fibular collateral ligament and biceps femoris; proximal tibiofibular joint.
Neck
Common fibular nerve winds around it — vulnerable to injury.
Shaft
Origins of fibularis longus/brevis, extensor digitorum longus, tibialis posterior, flexor hallucis longus, soleus.
Lateral malleolus
Lateral wall of the ankle mortise; lateral ankle ligaments attach.

Anatomy

Articulations: Tibia (proximal tibiofibular synovial joint; distal tibiofibular syndesmosis), talus (ankle joint).
Ossification: Primary centre ≈week 8. Distal epiphysis appears ≈1 year (fuses ≈15–18 years); proximal epiphysis ≈3–4 years (fuses ≈17–20 years) — an exception to the rule that the epiphysis appearing first fuses last.

Function

Forms the lateral wall of the ankle mortise, stabilising the talus
Attachment for leg muscles and the interosseous membrane
Bears a small fraction of body weight

Clinical significance

Fibular neck fracture / common fibular nerve injury

Trauma, tight casts or prolonged leg-crossing compress the common fibular nerve at the neck → foot drop (high-stepping gait), weakened eversion and numbness over the dorsum of the foot and lateral leg.

Ankle fractures (Weber classification)

Lateral malleolus fractures are classified by level relative to the syndesmosis: Weber A below (stable), B at the level, C above (syndesmosis disrupted, unstable). A Maisonneuve fracture — proximal fibular fracture with medial ankle injury — indicates syndesmotic disruption.

Fibular graft

Because it bears little weight, the fibular shaft is used as a vascularised free flap (peroneal artery) for mandible and long-bone reconstruction.

Test yourself

In a typical inversion sprain of the ankle, which ligament is usually torn first?

Deltoid ligament
Calcaneofibular ligament
Anterior talofibular ligament
Posterior talofibular ligament

Answer: Anterior talofibular ligament

The anterior talofibular ligament is the weakest lateral ligament and is taut in plantarflexion, so it is the first to tear in inversion–plantarflexion injuries; the calcaneofibular ligament tears next; the posterior talofibular ligament is rarely involved.