The tibia and fibula are connected bones that begin below the knee and end at the ankle, says Innerbody. The tibia is the larger and stronger bone, while the fibula, though as long as the tibia, is a slender bone attached to the side of the tibia.
At the top of the tibia are areas that attach to both the kneecap, formally called the patella, and the femur, which is the thigh bone, says Innerbody. They include the anterior intercondylar area, the lateral and medal condyle and the superior articular surface. A structure called the tibial tuberosity allows the patella to be attached to the tibia. Beneath these structures is the body of the tibia bone, which contains areas such as the anterior and medial border, the interosseous border and the lateral and medial surfaces.
At the bottom of the tibia bone is the medial malleolus, a somewhat hook-shaped projection of the bone, and several articular surfaces, claims the American Academy of Orthopaedic Surgeons.
The fibula has a head and neck and an anterior and posterior border, says Innerbody. It also has an anterior border, a lateral surface and a lateral malleolus. The fibula also has a fossa of malleolus, says Drugs.com. In contrast to the tibia, whose job is to support the body from the knees to the ankles, the fibula is there to support the tibia.