Anatomy of the Foot

Nearly one-fourth of the body's bones are in our feet. The bones of the feet are:

• Talus – the bone on top of the foot that forms a joint with the two bones of the lower leg, the tibia and fibula.
• Calcaneus – the largest bone of the foot, which lies beneath the talus to form the heel bone.
• Tarsals – five irregularly shaped bones of the midfoot that form the foot's arch. The tarsal bones are the cuboid, navicular and medial, intermediate and lateral cuneiforms.
• Metatarsals – five bones (labeled one through five, starting with the big toe) that make up the forefoot.
• Phalanges (singular: phalanx) – the 14 bones that make up the toes. The big toe consists of two phalanges – the distal and proximal. The other toes have three.
• Sesamoids – two small, pea-shaped bones that lie beneath the head of the first metatarsal in the ball of the foot.

Joints in the feet are formed wherever two or more of these bones meet. Except for the big toe, each of the toes has three joints, which include:

• Metatarsophalangeal joint (MCP) – the joint at the base of the toe
• Proximal interphalangeal joint (PIP) – the joint in the middle of the toe
• Distal phalangeal joint (DP) – the joint closest to the tip of the toe.

Each big toe has two joints:

• Metatarsophalangeal joint
• Interphalangeal joint

The surfaces of the bones where they meet to form joints are covered with a layer of cartilage, which allows them to glide smoothly against one another as they move. The joints are enclosed by a fibrous capsule that is lined with a thin membrane called the synovium, which secretes a fluid to lubricate the joints.

Twenty muscles give the foot its shape, support and the ability to move. The main muscles of the foot include the:

• Tibilias posterior , which supports the foot's arch
• Tibilias anterior , which allows the foot to move upward
• Tibilias peroneal , which controls movement on the outside of the ankle
• Extensors , which help raise the toes, making it possible to take a step
• Flexors , which help stabilize the toes.

Many tendons attach these muscles to the bones and ligaments that hold the bones together to maintain the foot's arch.

The main tendon of the foot is the Achilles tendon , which runs from the calf muscle to the heel. The Achilles tendon makes it possible to run, jump, climb stairs and stand on your toes.

The main ligaments of the foot are:

• Plantar fascia – the longest ligament of the foot. The ligament, which runs along the sole of the foot, from the heel to the toes, forms the arch. By stretching and contracting, the plantar fascia helps us balance and gives the foot strength for walking.
• Plantar calcaneonavicular ligament – a ligament of the sole of the foot that connects the calcaneus and navicular and supports the head of the talus.
• Calcaneocuboid ligament – the ligament that connects the calcaneus and the tarsal bones and helps the plantar fascia support the arch of the foot.