Each of your feet contains 26 bones. The ankle bone, known as the talus, and the ends of the two lower leg bones, called the tibia and fibula, form the ankle joint. This joint is supported and stabilized by three groups of ligaments.
The job of the ligaments is to hold the bones and joint in place. They protect the ankle joint from abnormal movements such as extreme twisting, turning, and rolling of the foot. Ligaments are elastic so they usually stretch within their limits, and then go back to their normal positions. However, when a ligament is forced to stretch beyond its normal range, a sprain occurs. A severe sprain can actually cause tearing of the elastic fibers.
Muscles, tendons and cartilage are other important components of your ankle. The job of the muscles and tendons is to move your foot and ankle. The tendons attach the muscles to bone, and the cartilage cushions your joints.