Fibula

The fibula is the slender lateral bone of the leg that runs alongside the larger tibia. Although it bears very little of the body's weight—approximately 10-15%—it plays important roles in providing attachment points for numerous muscles of the leg and foot, contributing to the lateral stability of the ankle joint through the lateral malleolus, and forming part of the ankle (talocrural) joint.

The lateral malleolus is the bony prominence at the lower end of the fibula that forms the outer bump of the ankle. It acts as a lateral stabilizer of the ankle joint, preventing excessive inversion. Fractures of the lateral malleolus are the most common ankle fractures, typically occurring with inversion injuries, and are classified using the Weber system based on the fracture level relative to the ankle joint syndesmosis.

The Weber (Danis-Weber) classification categorizes fibular fractures by their relationship to the syndesmosis—the fibrous joint connecting the fibula to the tibia above the ankle. Weber A fractures are below the syndesmosis and typically stable. Weber B fractures occur at the level of the syndesmosis and may be stable or unstable. Weber C fractures are above the syndesmosis and are generally unstable, often requiring surgical fixation.

The fibula is an excellent bone graft donor because it can be harvested with its blood supply (vascularized fibular graft) from the peroneal artery and veins. A substantial length can be removed without significantly compromising lower limb function, since the tibia bears the majority of weight. It is used to reconstruct the jaw, radius, femur, and other bones after tumor resection or trauma.

Numerous muscles of the leg originate from or insert on the fibula. These include the peroneus (fibularis) longus and brevis on the lateral aspect, the extensor digitorum longus and extensor hallucis longus on the anterior aspect, and the flexor hallucis longus, tibialis posterior, and peroneus tertius on the posterior and anterior aspects. The fibula head also provides attachment for the biceps femoris tendon.