The fibula is a long bone in the lower extremity that is positioned on the lateral side of the tibia. The fibula is much smaller and thinner than the tibia. It is located just behind the tibial head at the knee joint and then runs down the lateral aspect of the leg until it reaches the ankle joint. A ridge on the medial surface of the fibula forms the interosseous border where the fibula is connected to the tibia via the interosseous membrane. This connection forms a syndesmotic joint, meaning it has very little mobility.
The structure of the fibula can be broken down into the head, neck, shaft, and distal end of the fibula. As the head becomes narrow distally, the fibular neck is formed. The fibular shaft lies distal to the neck and has three surfaces, lateral, medial, and posterior. The shape of the fibular shaft is determined by the muscle attachments. Initially, it is a triangular shape and distally becomes more irregularly shaped. The distal end of the fibula forms the lateral malleolus which articulates with the lateral talus, creating part of the lateral ankle. The posterior and lateral tibia form the posterior and medial malleolus, respectively.
Like the tibia, the fibula is ossified in three areas, in the middle and at either end of the epiphysis. Ossification of the fibula begins in the shaft at around the eighth week of gestation and then extends to either end. The process of ossification is complete by the second decade of life. Both ends of the fibula remain cartilaginous.
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