Anatomy of the Foot and Ankle
What is the Normal Anatomy of the Foot and Ankle?
The foot and ankle form complex joints that are involved in movement and providing stability and balance to the body. The foot and ankle consist of 26 bones, 33 joints, and many muscles, tendons, and ligaments.
Bones of the Ankle
The ankle joint connects the leg with the foot and is composed of three bones: the tibia, fibula, and talus. The tibia or shinbone and fibula or calf bone are bones of the lower leg, which articulate with the talus or ankle bone, enabling up and down movement of the foot.
Three bony bumps present on the ends of the tibia and fibula form parts of the ankle joint:
- The medial malleolus, formed by the tibia, is found on the inside of the ankle.
- The posterior malleolus, also formed by the tibia, is found at the back of the ankle.
- The lateral malleolus, formed by the fibula, is found on the outer aspect of the ankle.
Bones of the Feet
The foot acts as a single functional unit, but can be divided into three parts: the hindfoot, midfoot and forefoot.
The hindfoot forms the ankle and heel, and is made up of the talus bone and calcaneus or heel bone. The heel bone is the largest bone in the foot.
The midfoot connects the hindfoot to the forefoot, and consists of one navicular bone, one cuboid bone, and three cuneiform bones. The navicular bone is found in front of the heel bone, and the cuneiform and cuboid bones are arranged in front of the navicular bone.
These bones are connected to five metatarsal bones of the forefoot that form the arch of the foot for shock absorption while walking or running. The forefoot is also made up of the toes or digits, formed by bones called phalanges - three in each toe, except the big toe, which has only two phalanges. The big toe has two additional tiny round sesamoid bones in the ball of the foot, which helps in upward and downward movements of the toe.
Ankle and Foot Joints
There are 33 joints in the ankle and foot. They include:
- Hinge joints in the ankle, which allow flexion (bending) and extension
- Gliding joints found in the hindfoot, which allow gliding movements
- Condyloid joints found in the forefoot and toes, which allow the flexion (bending) and extension, adduction, and abduction (sideward movement).
The joints of the foot and ankle provide stability and support the weight of your body, helping you to walk or run, and adapt to uneven grounds.
Soft Tissues of the Ankle and Foot
Our feet and ankle bones are held in place and supported by various soft tissues such as cartilage, ligaments, muscles, tendons, and bursae.
The joint surface of all the bones of the ankle and foot are lined by a thin, tough, flexible, and slippery surface called the articular cartilage, which acts as a shock absorber and cushion to reduce friction between the bones. The cartilage is lubricated by synovial fluid, which further enables smooth movement of the bones.
Ligaments are tough rope-like tissue that connect bones to other bones, and hold them in place, providing stability to the joints. The plantar fascia is the largest ligament in the foot, originating from the heel bone to the forefoot, it extends along the lower side of the foot and is involved in maintaining the arch of the foot. The plantar fascia ligament stretches and contracts to provide balance and strength to the foot. Lateral ligaments on the outside of the foot and medial ligaments on the inside of the foot provide stability and allow up and down movement of the foot.
The foot is made up of 20 muscles that help in movement. The main muscles include:
- Anterior tibial muscle, which allows up and down movement of the foot
- Posterior tibial muscle, which supports the arch
- Peroneal tibial muscle, which controls movement on the outside of the ankle
- Extensors, which enable the ankle to raise the toes just before stepping forward
- Flexors, which stabilize the toes against the floor
- Smaller muscles that help the toes to lift and curl
Tendons are soft tissues that connect muscles to bones. The largest and strongest tendon in the foot is the Achilles tendon, present at the back of the lower leg around the heel bone. Other tendons include peroneal and anterior and posterior tibialis.
Bursae are small fluid-filled sacs that decrease friction between tendons and bone or skin. They contain special cells called synovial cells that secrete a lubricating fluid.
Foot & Ankle Conditions
Inflammation of the Achilles tendon is known as Achilles tendinitis or tendonitis. The Achilles tendon is a tough band of fibrous tissue that runs down the back of your lower leg and connects your calf muscle to your heel bone. The tendon is used when you walk, climb, jump, run and stand on your tip toes.
A sprain is the stretching or tearing of ligaments. Ligaments connect adjacent bones and provide stability to a joint. An ankle sprain is a common injury that occurs when you suddenly fall or twist the ankle joint, or when you land your foot in an awkward position after a jump. Most commonly, it occurs when you participate in sports, or jump or run on a surface that is irregular.
An ankle ligament injury, also known as an ankle sprain, can be caused by a sudden twisting movement of the foot during any athletic event or during daily activities. When stretched beyond its limit, the ligament may partially or completely tear. The injury can range from mild to severe, depending on the condition of the injured ligament and the number of ligaments involved.
Achilles tendon bursitis or retrocalcaneal bursitis is a condition that commonly occurs in athletes. It is a painful condition caused by the swelling of the bursa, a fluid-filled sac that is located at the back of the heel under the Achilles tendon. This retrocalcaneal bursa contains a lubricating fluid that acts as a cushion to reduce friction between muscle and bones.
Arthritis is the inflammation of joints as a result of degeneration of the smooth cartilage that lines the ends of bones in a joint. This degeneration of the cartilages leads to painful rubbing of the bones, swelling, and stiffness in the joints, resulting in restricted movements. Arthritis in the foot and ankle can occur due to fractures, dislocation, inflammatory disease, or congenital deformity.
Foot pain occurs from distress induced by certain factors on the foot. It is a common problem experienced by young athletes involved in various activities such as running and jumping. Normally, foot pain can be treated with home treatments and may take time to heal. However, in cases of severe injury, adequate evaluation and treatment are required.
The foot is composed of bones, ligaments, nerves, muscles, and tendons. Nerve conditions of the foot can range from minor nerve injuries to serious conditions like nerve entrapment and damage. A podiatrist is a doctor specializing in the treatment of foot problems including nerve conditions.
Foot & Ankle Procedures
Foot injections are steroids that are injected into your foot to relieve pain and inflammation. Cortisol is a hormone that is produced in the human body and functions to reduce stress and inflammation. Steroids are synthetic drugs that resemble cortisol and are used in treating joint pain.
Compression stockings are snug-fitting sleeves or socks worn over the lower limbs and designed mainly for compression therapy. They fit firmly against your skin and help by applying moderate pressure, softly squeezing your legs. This helps the blood to flow from your legs back up to your heart and can reduce pain and swelling in your ankles and legs.