Picture of the metatarsal (foot) and calcaneus (heel) bones, the plantar fascia ligament, and the Achilles tendon of the lower leg and foot

The ankle is a “hinged” joint capable of moving the foot in two primary directions: away from the body (plantar flexion) and toward the body (dorsiflexion). The meeting of three bones forms its anatomy. The end of the shinbone of the leg (tibia) and a small bone in the leg (fibula) meet a large bone in the foot, called the talus, to form the ankle. The end of the shinbone (tibia) forms the ankle’s inner portion, while the end of the fibula forms the outer part of the ankle. The hard, bony knobs on each side of the ankle are called the malleoli. These provide stability to the ankle joints, functioning as weight-bearing joints for the body during standing and walking.

Ligaments on each side of the ankle also provide stability by tightly strapping the outside of the ankle (lateral malleolus) with the lateral collateral ligaments and the inner portion of the ankle (medial malleolus) with the medial collateral ligaments. A fibrous joint capsule surrounds the ankle joint. Tendons that attach the large muscles of the leg to the foot wrap around the ankle both from the front and behind. The large tendon (Achilles tendon) of the calf muscle passes behind the ankle and attaches to the heel’s back. A large tendon of the leg muscle (posterior tibial tendon) passes behind the medial malleolus. The peroneal tendon passes behind the lateral malleolus to attach to the foot.

The healthy ankle can move the foot, from the neutral right-angle position to approximately 45 degrees of plantar flexion, and around 20 degrees of dorsiflexion. The powerful muscles that move the ankle are located in the front and back portions of the leg. These muscles contract and relax during walking.