Ankle Anatomy and Physiology

The ankle and foot are complex structures, with a variety of connecting bones, ligaments, tendons, and muscles. The ankle is the joint where the foot attaches to the bones of the lower leg, allowing the foot to move up and down and side to side. It is the hinge that supports your body weight and takes the impact when you walk, run, or jump. The ligaments, tendons, and muscles provide stability and balance. Injuries or weakness of your ankle will affect your gait and your ability to walk smoothly and pain-free.

Bones and Joints of the Ankle

The ankle joint includes three bones (the tibia, the fibula, and the talus) that form a joint that allows the foot to bend up and down. This joint is a synovial hinge joint.

There are also other bones and joints that help stabilize and support the ankle joint.

Two bones of the foot (the talus and the calcaneus) connect to make the subtalar joint that allows the foot to move side to side. This joint allows you to stabilize the foot on uneven ground and stabilizes the ankle. The tarsal bones connect to the 5 long bones of the midfoot—the metatarsals.

The medial malleolus is on the inside of your ankle, and the lateral malleolus is on the outside of your ankle.

Ligaments and Tendons of the Ankle

The large Achilles tendon is the most important tendon for walking, running, and jumping. It attaches the calf muscles to the heel bone to allow us to push off and up on the toes.

A tear or rupture to the Achilles takes a long time to heal. There are another 9 tendons that cross the ankle. They are responsible for movements of the ankle, foot, and toes; some of these tendons also help support the arches of the foot.

An ankle sprain is an injury to one of the ligaments. The most common ankle sprain is a sprain of the anterior talofibular ligament. The calcaneofibular ligament can also be injured in an ankle sprain.

Muscles of the Ankle

The muscles of the foot are classified as intrinsic and extrinsic.

The intrinsic muscles are located within the foot and they are flexors (plantar flexors), extensors (dorsiflexors), abductors, and adductors of the toes. Several intrinsic muscles also help support the arches of the foot. They also micro-adjust the extrinsic muscles to align them in the proper direction, and they stabilize by giving isometric tension on the arch and joints.

The extrinsic muscles are located outside the foot, in the lower leg. The gastrocnemius muscle (calf) is the largest. They have long tendons that cross the ankle, to attach to the bones of the foot and assist movement.