What is the Normal Anatomy of the Foot and Ankle?
The foot and ankle are a complex joint 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: 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.
- Posterior malleolus, also formed by the tibia, is found at the back of the ankle.
- 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, which 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 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 help in upward and downward movement 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 the body, helping you to walk or run, and to adapt to uneven ground.
The joint surface of all bones of the ankle and foot are lined by a thin, tough, flexible, and slippery surface called 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.
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.
Cartilage is the flexible, shiny, smooth tissue on the ends of bones that meet to form a joint. Cartilage provides cushioning between the bones allowing smooth movement.
Ligaments are tough rope-like tissue that connect bones to other bones, and holds 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 bottom surface 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, which help in movement. The main muscles include:
- Anterior tibial muscle: allows up and down movement of the foot
- Posterior tibial muscle: supports the arch
- Peroneal tibial muscle: controls movement on the outside of the ankle
- Extensors: enable the ankle to raise the toes just before stepping forward
- Flexors: stabilize the toes against the floor
- Smaller muscles are also present to help the toes 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. Bursae contain special cells called synovial cells that secrete a lubricating fluid.
Flatfoot, also known as "fallen arches" or Pes planus, is a deformity of the feet in which the arch that runs lengthwise along the sole of the foot collapses to the ground or is not formed at all.
Sports injuries occur when playing indoor or outdoor sports or while exercising. They can result from accidents, inadequate training, improper use of protective devices, or insufficient stretching or warm-up exercises. The most common sports injuries are sprains and strains, fractures and dislocations
Ankle instability is a chronic condition characterized by a recurrent slipping of the outer side of the ankle. It usually results from repeated ankle sprains. It is generally noticed during movement of the ankle joint but can also occur during standing as well.
The Achilles tendon is a strong, fibrous cord present behind the ankle that connects the calf muscles to the heel bone. It is used when you walk, run and jump. The Achilles tendon injuries most often in athletes participating in sports that involve running, pivoting and jumping. Recreational sports that may cause Achilles rupture include tennis, football, basketball and gymnastics.
A bunion, also known as hallux valgus, is bony prominence at the base of the big toe, which often results in pain, redness and rubbing in footwear. The first metatarsal bone abnormally angles outward towards the other foot from its joint in the midfoot.A bunion can change the shape of your foot, make it difficult for you to find shoes that fit correctly and worsen the symptoms if left untreated.
Diabetes is a chronic condition that is characterized by high blood glucose (sugar) levels. Diabetic patients are at a high risk for developing chronic wounds, especially in the feet. If left untreated, these wounds can cause serious problems that can lead to infections and eventually gangrene, which may require amputation.
A sprain is the stretching or tearing of ligaments, which connect adjacent bones and provide stability to a joint. An 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 when you jump or run on a surface that is irregular.
Plantar fasciitis refers to inflammation of the plantar fascia, a thick band of tissue that is present at the bottom of the foot. It runs from the heel bone to the toe and forms the arch of your foot. Plantar fasciitis is one of the most common causes of heel pain. It is most often seen in middle-aged men and women, but may also occur in those who are constantly on their feet.
Ankle injuries are very common in athletes and in people performing physical work, often resulting in severe pain and impaired mobility. Pain after ankle injuries can either be from a torn ligament and is called an ankle sprain or from a broken bone which is called an ankle fracture. An ankle fracture is a painful condition where there is a break in one or more bones forming the ankle joint. The ankle joint is stabilized by different ligaments and other soft tissues, which may also be injured during an ankle fracture.
Trauma and repeated stress can cause fractures in the foot. Extreme force is required to fracture the bones in the hind foot. The most common type of foot fracture is a stress fracture, which occurs when repeated activities produce small cracks in the bones.
Foot and ankle trauma refers to the injuries that most commonly occur during sports, exercise or any other physical activity. Trauma may be a result of accidents, poor training practices or use of improper gear. Injuries may also be caused when an individual is not medically fit or because of insufficient warm up and stretching exercises.
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. It is one of the most common orthopaedic injuries and can also be caused by walking down a slope or over any uneven surface. The injury can range from mild to severe, depending on the condition of the injured ligament and the number of ligaments involved.
Arthritis is inflammation resulting from the degeneration of cartilage in the joint causing joint pain, swelling, and stiffness resulting in restricted movements. Arthritis of the foot and ankle joint can occur due to fractures, dislocation, inflammatory disease, or congenital deformity.
Achilles tendon bursitis or retrocalcaneal bursitis is a condition that commonly occurs in athletes. It is a painful condition caused by swelling of the bursa, a fluid-filled sac which 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. The Achilles tendon is the large tendon that connects the calf muscles to the heel bone (calcaneus) and is used when you walk, run and jump.
Ankle replacement is a procedure performed to replace the damaged ankle joint with an artificial joint. Ankle replacement is generally carried out to treat arthritic conditions such as osteoarthritis or rheumatoid arthritis in which the ankle joint wears out or becomes inflamed and painful.
Tendons are the soft tissues connecting muscle to bone. The Achilles tendon is the longest tendon in the body and is present behind the ankle, joining the calf muscles with the heel bone. Contraction of the calf muscles tightens the Achilles tendon and pulls the heel, enabling the foot and toe movements necessary for walking, running and jumping.
Ankle fractures result from excessive rolling and twisting of the ankle, usually occurring from an accident or activities such as jumping or falling, causing sudden stress to the joint.
The posterior tibial tendon passes through the ankle to attach the calf muscle with the bones of the mid foot. It provides stability to the arch and supports the foot while walking. Inflammation or a tear of this tendon as a result of injury may cause dysfunction, leading to pain and the development of flatfoot.
Ankle fusion (arthrodesis) is the surgical fusion of bones that form the ankle joint. The ankle joint is formed by the tibia, talus and the fibula bones. The goal of ankle arthrodesis is to relieve pain in the affected joint by surgically eliminating the joint.
The hindfoot consists of the talus bone or ankle bone and the calcaneus bone or heel bone. The talus bone is the highest bone in the foot while the calcaneus bone is the largest bone in the foot. The calcaneus joins the talus bone at the subtalar joint enabling the foot to rotate at the ankle.