The average person takes about 8,000 to 10,000 steps a day. In a lifetime, the average person has likely walked enough to go around the circumference of the world four times.
The foot and ankle is a complex mechanism. The foot contains 26 bones, 33 joints, 107 ligaments and 19 muscles. The two most important functions of the foot are to bear weight and propel a person. The components of the ankle along with the muscles and tendons of the lower leg all work together to handle the stress the ankle has when a person walks, runs or jumps. A problem with any one of these parts can cause pain and difficulties with foot and ankle functions.
The ankle joint, called the tibiotalar joint, consists of three major bones: the tibia, fibular and talus. The tibia is the large shinbone; it forms the inside part of the ankle. The fibula is the smaller calf bone that forms the outside part of the ankle. The talus is the bone on the top of the foot that connects the ankle to the foot. This joint allows the foot to move up and down.
The subtalar joint is the primary joint of the hindfoot located just below the ankle joint. It consists of two major bones: the talus and calcaneus. The talus is the bone on the top of the foot, and the calcaneus is the heel bone. This joint allows the foot to move side to side.
The other foot joints include:
- The talonavicular joint is where the talus connects to the naviculus, or the inner midfoot bone.
- The calcaneocuboid joint is where the heel bone connects to the cuboid, or the outer midfoot bone.
- The metarsocunieform joint is where one of the metatarsals, or forefoot bones, connects to the smaller midfoot bones.
- The first metatarsophalangeal joint is where the first forefoot bone connects to the phalanx, or toe bone.
The ends of the bones are covered by articular cartilage. The hard, slick material helps reduce friction between the bones during movement.
The bones of the foot and ankle are joined to the other bones by short bands of tough fibrous connective tissue called ligaments. They give the joints strength and stability.
There are several major ligaments in the foot and ankle. Some of the more important ones include the following:
- The anterior tibiofibular ligament connects the tibia to the fibula.
- The lateral ligaments are three ligaments along the outside of the ankle that connect the fibula, talus and calcaneus. These are the ligaments most commonly injured in an ankle sprain.
- The deltoid ligament, or the medial ligament, is a thick and strong ligament on the inside of the ankle. It attaches the tibia to the talus and calcaneus.
Muscles and Tendons
The muscles of the foot are either intrinsic or extrinsic muscles, and are responsible for causing movement and to provide stability during activities. The intrinsic muscles are located within the foot and cause movement of the toes. Extrinsic muscles are located outside the foot in the lower leg.
The gastrocnemius muscle, or main calf muscle, is an extrinsic muscle. It allows a person to point the foot and stand on tip-toe. The peroneal muscles are on the outside of the legs; they provide stability and allow the foot to turn out. Other muscles help a person extend the foot and toes.
Muscles have tendons, which connect muscles to bones. The larger Achilles tendon is critical. It attaches the calf muscle to the heel bone, and it is responsible for allowing a person to walk, run and jump. The posterior tibial tendon attaches one of the smaller muscles of the calf to the underside of the foot. This tendon supports the arch. The anterior tibial tendon allows the foot to be raised. The muscles of the toes also have tendons.