Knee ligament surgery. 3D computed tomography (CT) scan of a knee being assessed for ligament surgery. The knee joint is formed by the femur (thigh bone, top), the patella (knee-cap) and the two lower leg bones (tibia, lower centre; and fibula, lower right). The angle shown here helps surgeons decide where to place the screws used during the operation, which reconstructs the ligaments and stabilises the knee joint. Ligaments are fibrous bands that connect bones to other bones. Image obtained using the Vesalius3D scanning technique.