The ankle, a hinge joint, is made up of three bones: the tibia, fibula, and talus. The tibia is the larger of the two bones in the lower leg. The tibia’s lower end flares out, forming a hard, bony knob, called the medial malleolus on the inside of the ankle. The fibula’s lower end forms a hard, bony knob, called the lateral malleolus, on the outside of the ankle. The talus is a wedge-shaped bone deep inside the ankle between the heel bone and the ends of the tibia and fibula that forms a solid base for ankle movement.
The ends of the bones are covered with articular cartilage. Ligaments, strong, fibrous tissues, connect bones to other bones and stabilize the joint. The ankle must be stable in order to withstand 1.5 times the body weight when walking and up to 8 times when running.