Ankle

From ArticleWorld

The ankle is the joint in the distal lower extremity of humans that connects the calf or lower leg to the foot. The ankle joint actually consists of two separate joints which together allow several different movements of the joint.

Anatomy

The topmost joint of the ankle is called the talocrural joint. It is formed by the distal ends of the tibia and fibula and the proximal end of the talus bone. This joint is responsible for plantar flexion and dorsiflexion (or pointing upward) of the foot.

The lowermost joint of the ankle is made from the lower surface of the talus and the uppermost surface of the calcaneus (heel) bone. This joint allows for the inversion (turning inward) of the foot and eversion (outward turning) of the foot.

Multiple ligaments support the joint. The anterior talofibular ligament and the posterior talofibular ligament support the lateral aspect of the ankle joint. The deltoid ligament and the plantar calcaneonavicular ligament support parts of the medial aspect of the ankle joint.

Function

The muscles that allow for movement about the ankle are located primarily in the calf. The strong gastrocnemius muscle attaches to a bony prominence on the calcaneus and allows for a powerful plantar flexion that allows an individual to take the entirety of their body’s weight on the distal part of the foot near the toes.

The dorsiflexion of the ankle joint is partly performed by the tibialis anterior muscle. The distal aspect of the tibia and the ankle joint itself have two separate fibrous bands that keep the various tendons for both ankle and toe movement in place. They are the superior extensor retinaculum and the inferior extensor retinaculum.

Smaller muscles of the foot, as well as some of the calf muscles allow for inversion or eversion of the ankle. Eversion and inversion are not generally actively done in the process of walking. In fact, inversion of the foot while walking is a common cause of ankle injury.

Conditions

The ankle is a frequent place of injury during sports or as a result of a misstep. The most common injury is an ankle sprain involving an inversion of the foot while walking. This results in a tear or strain of the anterior talofibular ligament and sometimes the posterior talofibular ligament as well. A serious injury fractures the distal end of the fibula. A very serious injury fractures the end of the fibula and aspects of the distal tibia as well. This results in instability of the proximal ankle joint that often requires surgical intervention.

The other ankle-related injury involves a rupture of the Achilles’ tendon when an individual has a strong gastrocnemius muscle that overcomes the ability of the tendon to hold fast to the calcaneus.