Tibia and fibula.
The fibula is the long thin outer bone of the lower leg of four- and two-legged vertebrates, including humans. The fibula takes no part in the articulation at the knee joint but, below, it forms the lateral malleolus of the ankle joint. It takes no part in the transmission of body weight, a task which falls to the other, and much sturdier, lower leg bone, the tibia. The fibula has an expanded upper end, a shaft, and a lower end.
The upper end, or head, is surmounted by a styloid process. It possesses an articular surface for articulation with the lateral condyle of the tibia.
The shaft of the fibula is long and slender, and its shape is subject to considerable variation. Typically, its has four borders and four surfaces. The anterior surface is very narrow in its upper part, where the anterior and medial borders run close together or may become confluent. The medial or interosseous border gives attachment to the interosseous membrane.
The lower end of the fibula forms the triangular lateral malleolus, which is subcutaneous. On the medial surface of the lateral malleolus is a triangular articular facet for articulation with the lateral aspect of the talus. Below and behind the articular facet is a depression called the malleolar fossa.
The main function of the fibula is to provide an attachment for muscles. It provides little supportive strength to the lower leg, which is why pieces of bone can safely be taken from it for grafting elsewhere in the body.
Fractures of the fibula
The fibula is one of the most commonly broken bones. Fracture of the fibula just above the ankle may occur with a severe ankle sprain as a result of a violent twisting movement. Pott's fracture is fracture of the fibula just above the ankle combined with dislocation of the ankle and sometimes with fracture of the tibia.
A suspected fracture of the fibula is X-rayed to confirm the diagnosis. In some cases the lower leg is immobilized in a plaster cast to allow the bone to heal. If the fracture occurs in the middle portion of the fibula, immobilization may not be needed. If the fracture is severe (especially if it is accompanied by dislocation of the ankle), surgery may be necessary to fasten the broken pieces of bone with metal pins.
A fractured fibula may take up to six weeks to heal, depending on its severity and the age of the patient.