The joint between the foot and lower leg is called the ankle joint and is composed mainly of the distal tibia, the distal fibula and the upper talus together. The ankle joint allows for flexion and extension, internal and external rotation, as well as mild rotation. The stability of the ankle joint decreases when going down steps, mainly because the joint surface at the posterior end of the talus is significantly narrower than the anterior end, which makes the ankle joint prone to sprain. The sprain is usually an inversion sprain and is prone to rupture of the lateral collateral ligament. The ankle joint is also susceptible to fractures under direct or indirect violence, including medial ankle fractures, external ankle fractures, and posterior ankle fractures. The ankle joint can bear weight normally, but arthritis and synovitis are likely to develop within the ankle joint, and patients may experience painful symptoms.