Fibula: the slender bone of the lower leg

Structure and articulations

The fibula is typically described with a head at its proximal end, a long shaft, and a prominent distal projection called the lateral malleolus. Proximally it articulates with the tibia at the proximal tibiofibular joint; distally it helps form the ankle by contributing the lateral malleolus that grips the talus. The bone does not directly articulate with the femur or the knee joint, though it provides attachment sites for structures near the knee.

Function and muscle attachments

The fibula is not the main weight‑bearing bone of the leg—that role belongs to the tibia—but it plays important roles in stabilizing the leg and ankle and serving as an attachment site for muscles. Several calf and foot muscles originate from or attach to the fibula, including the fibularis (peroneus) muscles and parts of the soleus and tibialis muscles. The head of the fibula is a site where the tendon of the biceps femoris and ligaments attach, contributing to lateral stability.

Development and evolution

During human growth the fibula ossifies from centers in the shaft and ends and matures through childhood into adolescence. In evolutionary terms the fibula appears throughout tetrapod lineages but shows modification: in some birds and cursorial mammals it is reduced or fused, whereas in many reptiles and amphibians it retains a form similar to the tibia.

Clinical significance

Fractures of the fibula are common, often in combination with ankle injuries. Because the common fibular (peroneal) nerve wraps around the fibular neck, trauma there can affect nerve function and produce sensory changes or weakness of dorsiflexion. The fibula is also frequently used in reconstructive surgery as a donor for bone grafts because of its length and relative expendability.

Distinctions and notable facts

• The fibula is slender and lateral, while the tibia is broad and medial.
• It contributes the lateral malleolus that stabilizes the ankle joint.
• In comparative anatomy the bone’s form varies; see resources on limb bones in tetrapods and the human lower leg.
• Above the leg are the femur and knee complex; the fibula supports but does not directly bear the knee joint.