Foot & Ankle
Foot & Ankle Anatomy
The foot and ankle is a complex series of bones and joints involved in the provision of movement and stability to the body. The foot and ankle consists of 28 bones, 33 joints, and many muscles, tendons and ligaments.
Bones of the Ankle
The ankle joint (or ‘talocrural joint’) connects the leg with the foot, and comprises three bones: the tibia, fibula and talus. The tibia (shin bone) and fibula are the lower leg bones which articulate with the talus, enabling up and down movement of the foot (dorsiflexion and plantarflexion).
Two bony prominences present on either side of the ankle:
- The medial malleolus, formed by the tibia, is found on the inside of the ankle;
- The lateral malleolus, formed by the fibula, is found on the outside 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 and the calcaneus (heel bone). The heel bone is the biggest bone in the foot.
The midfoot connects the hindfoot to the forefoot, and consists of the navicular, the cuboid, and three cuneiform bones. The navicular is found in front of the talus, the cuboid is in front of the calcaneus, and the cuneiforms complete the rest of the midfoot.
These bones are connected to the 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. Each toes is formed by three phalanges, except the big toe which only has two phalanges. The big toe has two additional tiny bones under the ball of the foot called sesamoids, which help in flexion and extension of the toe.
Ankle and Foot Joints
There are 33 joints in the ankle and foot. They include the
- Hinge joints in the ankle, which allow flexion and extension
- Gliding joints found in the hindfoot, which allow side-to-side movements
- Condyloid joints found in the forefoot and toes, which allow flexion and extension, adduction and abduction (sidewards 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 tissues that connect bones to other bones, and hold them in place to provide stability to the joints. The plantar fascia is the largest ligament in the foot, spanning from the heel bone to the forefoot. It is involved in maintaining the longitudinal arch of the foot. The lateral ligaments on the outside of the ankle (ATFL, CFL and PTFL) and medial ligament (deltoid ligament) on the inside of the ankle provide stability to the ankle joint.
The foot is made up of 20 muscles, which help in movement. The main muscles include:
- Tibialis Anterior muscle: pulls the foot upwards (dorsiflexion).
- Tibialis Posterior muscle: supports the arch and allows you to stand on your forefeet.
- Peroneus longus and brevis muscles: controls movement on the outside of the ankle.
- Extensors: enables the ankle and toes to be raised.
- Flexors: allows the ankle and toes to be lowered.
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 and ankle is the Achilles tendon, present at the back of the lower leg. The Achilles tendon connects the calf muscles (gastrocnemius and soleus) to the heel bone. Other major tendons include those of the peroneus longus and brevis, tibialis anterior and tibialis posterior, extensor digitorum longus and extensor hallucis longus (toe extensors), and flexor digitorum longus and flexor hallucis longus (toe flexors).
A bursa is a small fluid-filled sac that decreases friction between tendons and bone or skin. Bursae contain special cells called synovial cells that secrete a lubricating fluid.