Your feet and ankles are built for durability. They are designed this way to account for the significant amount of pressure they withstand every time you perform an activity that involves standing. When running, for example, each foot takes on a force that can be as much as three times your body weight. As a result, the foot and ankle have an anatomy that is both beautiful and complex, and this complexity plays a major role allowing you to complete the movements necessary to navigate the world.
The anatomy of the ankle and foot are connected and very closely related. The ankle joint is made up of three bones:
- Tibia: the shinbone, the major bone of the lower leg, which is responsible for bearing most of the body’s weight
- Fibula: the other bone of the lower leg, which is thinner than the tibia and sits behind it; the fibula helps to stabilize the ankle and supports the surrounding muscles
- Talus: a small bone at the top of the foot that helps transfer weight and pressure forces across the ankle joint; the top of the talus is shaped like a dome and is completely covered by cartilage, which is a tough, rubbery tissue that allows the ankle to move smoothly
The talus is one of the 26 bones that make up the foot. On top of this basic structure, each foot also consists of 33 joints and more than 100 muscles, tendons, and ligaments. Tendons are cords of strong tissue that connect muscles to bones, with each muscle being connected to one or more bones of the foot by a tendon. Ligaments are flexible bands of tissue that connect bones to one another. In the ankle, they bind joints together and provide stability by limiting side–to–side movement. They are elastic structures, which means they can stretch within their limits and then return to their normal position.
Some of the other structures of the foot and ankle that are important for their movement and function include the following:
- Plantar fascia: a thick, connective band of soft tissue that stretches from the heel to the base of your toes at the ball of the foot; this strong ligament connects the bones in these two regions and is designed to absorb the significant amount of stress placed on the feet, and it can withstand a great deal of force
- Achilles tendon: this tendon connects the two calf muscles to the back of the heel bone, and it provides support and stability for the ankle when performing many common movements like walking and running; most of the force generated when pushing the toe off the ground during a running stride is transmitted to the Achilles, which can be as much as three times your body weight
- Two longitudinal arches: these arches span the length of the foot from the heel bone to behind the ball of the foot
- Medial longitudinal arch: runs across the inside of the foot
- Lateral longitudinal arch: runs across the outside of the foot
- One transverse arch: spans the width of the foot
These three arches are formed by the tarsus and the metatarsal bones in the middle of the foot, and their shape allows them to act like a spring for the rest of the body. Any time you are on your feet, the arches bear your body weight and absorb the shock placed on them when you move. This force is then sent back to the rest of the body during actions like running and jumping. The arches are also quite flexible, which helps the feet appropriately respond to just about any type of movement.
Read our next newsletter for a look at how these structures are involved in some of the most common foot and ankle injuries.