Fibula

The fibula is the second bone of the skeleton of the leg: it runs along the lateral border of the tibia and does not articulate with the femur proximally.

As the tibia carries the most of the weight of animal, the fibula is reduced: this reduction differs between species but is correlated as the reduction of the ulna in the thoracic limb. For example, the fibula is reduced  in diameter but not in length in carnivores, whereas in horses the distal part of fibula is completely fused with the tibia.

The fibula is divided into :

• A proximal extremity with the head
• A neck
• A body (shaft)
• A distal extremity forming the lateral malleolus (excepted in horses where the lateral malleolus belongs to the tibia because of the fusion of tibia and fibula)