Some anatomical features of the ankle include the calcaneus, or heelbone, the medial malleolus, the lower part of the tibia, the talus and the lateral malleolus. The lower part of the fibula also makes up part of the ankle. It forms a cavity with the lower part of the tibia, into which fits the uppermost bone of the foot.
There are a series of ligaments that hold together the ankle bones, such as the plantar ligament, the posterior talofibular and tibiofibular ligaments, and the anterior talofibular and tibiofibular ligaments. The deltoid and syndesmotic ligaments also help to keep the ankle stable. Besides providing stability, the ligaments of the ankle allow the foot to move up and down like a hinge.
The muscles that make up the ankle include the long extensor hallucis longus muscle, which stretches from the tibia down to the big toe, and the much shorter extensor hallucis brevis muscle. There are also the peroneus brevis and peroneus longus muscles. There are also many tendons, including the Achilles tendon, which is located at the back of the ankle and the nearby plantaris tendon.
The ankle is also full of mechanoreceptors, which send information to the central nervous system. Scientists believe that muscle spindles in the ankle are responsible for this function.