Foot & Ankle

The ankle is a hinge joint. The end of the shinbone (tibia) meets a bone in the foot called the talus. The thinner lower leg bone (fibula) is on the outside of the ankle and prevents the tibia from shifting outward. The ends of the two bones have a hard layer of cartilage to help them slide smoothly against each other. Ligaments keep the joint’s bones from moving out of place.

In addition to the talus, the foot bones include the calcaneus, tarsals, metatarsals, phalanges, and sesamoids. Joints are formed wherever two of these bones meet.

Twenty muscles provide support and stability while letting the foot move.

Tendons attach the muscles to the bones. The largest is the Achilles tendon, which runs from the calf muscles to the heel. The main ligaments that hold the bones together include the plantar fascia, plantar calcaneonavicular ligament, and the calcaneocuboid ligament.

The lower leg bones keep the talus in place, allowing the ankle to move smoothly back and forth. The joint is most stable when the foot is flat on the floor. The joint becomes unstable when the toes point down and the distance between the bony stabilizers of the ankle becomes larger and the ligaments must hold the ankle in place. Since the ligaments are "softer" than bones, the area becomes more vulnerable to a sprain when the toes are pointed.

When an ankle twists, one or more of the ligaments stabilizing the joint gets torn and damaged. This is called a sprain.

Injuries most commonly occur on these ligaments:

• The Anterior (meaning front) Talo-Fibular Ligament (ATFL) connects the fibula on the outside of the ankle to the front of the talus bone. This is the most common ligament that is torn when you twist your ankle.
• The Calcaneo-Fibular Ligament connects the heel bone to the fibula. This is the second most common injury site.

The following ligaments can also be damaged, though less frequently:

• The Posterior (meaning back) Talo-Fibular Ligament (PTFL) attaches the fibula to the back of the talus.
• The Tibiofibular Syndesmotic Ligament connects the fibula to the tibia.

The most common ankle break is in the small outer leg bone, called the fibula. But, when larger forces are applied to the ankle, both the fibula and tibia (shinbone) can break. These fractures cause severe ankle instability and may even dislocate the entire ankle joint.

Surgery may be needed, depending on the actual or potential dislocation of the ankle.