Normal Anatomy of the Foot & Ankle Joint
The foot and ankle in the human body work together to provide balance, stability, movement, and propulsion.
This complex anatomy consists of:
- 26 bones
- 33 joints
- Blood vessels, nerves, and soft tissue
In order to understand conditions that affect the foot and ankle, it is important to understand the normal anatomy of the foot and ankle.
The ankle consists of three bones attached by muscles, tendons, and ligaments that connect the foot to the leg.
In the lower leg are two bones called the tibia (shin bone) and the fibula. These bones articulate (connect) to the Talus or ankle bone at the tibiotalar joint (ankle joint) allowing the foot to move up and down.
- Tibia (shin bone)
- Lateral Malleolus
- Medial Malleolus
The bony protrusions that we can see and feel on the ankle are:
- Lateral Malleolus: this is the outer ankle bone formed by the distal end of the fibula.
- Medial Malleolus: this is the inner ankle bone formed by the distal end of the tibia.
The foot can be divided into three anatomical sections called the hind foot, mid foot, and forefoot. The hind foot consists of the Talus bone or ankle bone and the calcaneous bone or heel bone. The calcaneous bone is the largest bone in your foot while the talus bone is the highest bone in your foot. The calcaneous joins the Talus bone at the subtalar joint enabling the foot to rotate at the ankle.
The hind foot connects the mid foot to the ankle at the transverse tarsal joint.
The mid foot contains five tarsal bones: the navicular bone, the cuboid bone, and 3 cuneiform bones. It connects the forefoot to the hind foot with muscles and ligaments. The main ligament is the plantar fascia ligament. The mid foot is responsible for forming the arches of your feet and acts as a shock absorber when walking or running.
The mid foot connects to the forefoot at the five tars metatarsal joints.
- Cuneiform Bones
The forefoot consists of your toe bones, called phalanges, and metatarsal bones, the long bones in your feet. Phalanges connect to metatarsals at the ball of the foot by joints called phalange metatarsal joints. Each toe has 3 phalange bones and 2 joints, while the big toe contains two phalange bones, two joints, and two tiny, round sesamoid bones that enable the toe to move up and down. Sesamoid bones are bones that develop inside of a tendon over a bony prominence.
The first metatarsal bone connected to the big toe is the shortest and thickest of the metatarsals and is the location for the attachment of several tendons. This bone is important for its role in propulsion and weight bearing.
Soft Tissue Anatomy
Our feet and ankle bones are held in place and supported by various soft tissues.
- Cartilage : Shiny and smooth, cartilage allows smooth movement where two bones come in contact with each other.
- Tendons : Tendons are soft tissue that connects muscles to bones to provide support. The Achilles tendon, also called the heel cord, is the largest and strongest tendon in the body. Located on the back of the lower leg it wraps around the calcaneous, or heel bone. When inflamed it causes a very painful condition called Achilles tendonitis and can make walking almost impossible due to the pain.
- Ligaments : Ligaments are strong rope like tissue that connects bones to other bones and help hold tendons in place providing stability to the joints. The plantar fascia is the longest ligament in the foot, originating at the calcaneous, heel bone, and continuing along the bottom surface of the foot to the forefoot. It is responsible for the arches of the foot and provides shock absorption. A common cause of heel pain in adults, plantar fasciitis can occur when repetitive micro tears occur in the plantar fascia from overuse. Ankle sprains, the most commonly reported injury to the foot and ankle area, involve ligament strain, and usually occur to the talo-fibular ligament and the calcaneo-fibular ligament.
- Muscles : Muscles are fibrous tissue capable of contracting to cause body movement. There are 20 muscles in the foot and these are classified as intrinsic or extrinsic. The intrinsic muscles are those located in the foot and are responsible for toe movement. The extrinsic muscles are located outside the foot in the lower leg. The gastrocnemius or calf muscle is the largest of these and assists with movement of the foot. Muscle strains occur usually from overuse of the muscle in which the muscle is stretched without being properly warmed up.
- Bursae : 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. When this fluid becomes infected, a common painful condition known as Bursitis can develop.
Biomechanics of Foot & Ankle
Biomechanics is a term to describe movement of the body. The ankle joint by itself permits two movements:
flexion : Pointing the foot downward. This movement is normally accompanied by inversion of the foot.
- Dorsiflexion : Raising the foot upward. This movement is normally accompanied by eversion of the foot.
The foot (excluding the toes) also permits two movements:
- Inversion : Turning the sole of the foot inward.
- Eversion : Turning the sole of the foot outward
The toes allow four different movements:
- Plantar flexion : Bending the toes towards the sole of the foot
- Dorsiflexion : Bending the toes towards the top of the foot
- Abduction : Spreading the toes apart. This movement normally accompanies plantar dorsiflexion.
- Adduction : Bringing the toes together. This movement normally accompanies plantar flexion.