The foot and ankle are intricate structures composed of a network of bones and joints that are essential for movement and stability in the human body. These structures include 28 bones, 33 joints, and numerous muscles, tendons, and ligaments.

Ankle Bones

The ankle joint, also known as the talocrural joint, serves as the connection between the leg and foot. It involves three primary bones: the tibia, fibula, and talus. The tibia and fibula, which make up the lower leg, interact with the talus to facilitate the up-and-down motion of the foot, known as dorsiflexion and plantarflexion.

The ankle features two prominent bony structures:

Medial malleolus: Found on the inner side of the ankle, formed by the tibia.

Lateral malleolus: Located on the outer side of the ankle, formed by the fibula.

Foot Bones

The foot operates as a cohesive unit, but it can be divided into three regions: the hindfoot, midfoot, and forefoot.

• Hindfoot: This area forms the ankle and heel, consisting of the talus and the calcaneus (heel bone), with the latter being the largest bone in the foot.
• Midfoot: This segment links the hindfoot to the forefoot and is made up of the navicular, cuboid, and three cuneiform bones. The navicular is positioned in front of the talus, the cuboid is in front of the calcaneus, and the cuneiform bones complete the midfoot structure.
• Forefoot: Connected to the midfoot bones, the forefoot includes the five metatarsal bones, which form the foot’s arch, absorbing shock during activities like walking or running. The toes are also part of the forefoot, with each toe made up of three phalanges, except for the big toe, which has two. Additionally, the big toe has two small bones under the ball of the foot called sesamoids that assist in its movement.

Ankle and Foot Joints

There are 33 joints within the ankle and foot, including:

Hinge joints in the ankle, enabling flexion and extension.

Gliding joints in the hindfoot, allowing side-to-side movement.

Condyloid joints in the forefoot and toes, permitting flexion, extension, adduction, and abduction.

These joints contribute to the foot and ankle’s ability to stabilize, support body weight, and adapt to uneven surfaces. The surfaces of these joints are covered by articular cartilage, a thin, resilient layer that reduces friction and absorbs shock. This cartilage is lubricated by synovial fluid, which further facilitates smooth movement.

Soft Tissues of the Ankle and Foot

The bones of the foot and ankle are held together and supported by various soft tissues, including cartilage, ligaments, muscles, tendons, and bursae.

Cartilage: A smooth, flexible tissue that covers the ends of bones in joints, allowing them to move smoothly against each other.

Ligaments: Tough, fibrous tissues that connect bones to other bones, providing joint stability. Notable ligaments include the plantar fascia, which supports the foot’s arch, and the lateral (ATFL, CFL, PTFL) and medial (deltoid) ligaments that stabilize the ankle.

Muscles: The foot contains 20 muscles that facilitate movement. Key muscles include:

• • Tibialis Anterior: Elevates the foot.
  • Tibialis Posterior: Supports the arch and assists in standing on the forefoot.
  • Peroneus Longus and Brevis: Control movement on the ankle’s outer side.
  • Extensors: Raise the ankle and toes.
  • Flexors: Lower the ankle and toes.

Additionally, smaller muscles help with toe movements.

Tendons: These tissues connect muscles to bones. The Achilles tendon, the strongest and largest in the foot and ankle, links the calf muscles to the heel bone. Other significant tendons include those of the peroneus longus and brevis, tibialis anterior and posterior, as well as the extensor and flexor tendons of the toes.

Bursae

A bursa is a small, fluid-filled sac that reduces friction between tendons and bones or skin. These sacs are lined with synovial cells that secrete lubricating fluid, ensuring smooth interaction between these structures.