Collaboratively, the foot and ankle form one of the most complex structures in the human body, consisting of 26 bones, 33 joints, 20 muscles and 107 ligaments. The components of the foot and ankle constantly work together to allow individuals to perform some of life’s most essential functions – walking, running, standing up-right and jumping. These components must not only be strong enough to support the weight of the body and forces exerted on it, but also be limber enough to move precisely. Even a minor injury to any one of the foot or ankle’s parts can compromise the integrity of this crucial working dynamic. In order to understand the conditions associated with the foot and ankle, it is important to understand their anatomy.
The foot can be broken down into the three sections:
- The forefoot is comprised of the 5 phalanges (toes) and 5 metatarsals (longer bones).
- The midfoot is comprised of the three cuneiform bones, the cuboid bone and the navicular bone. Here they come together in a pyramid-like shape to form the arches of the feet.
- The hindfoot is comprised of two large bones, the talus bone which supports the tibia and fibula and forms the ankle and the calcaneus bone or heel bone – the largest bone in the foot.
The ankle’s primary joint is a hinge synovial joint responsible for the articulation between the tibia, fibula and talus. There are also three main joints of the foot: the subtalar, talocalcaneonavicular and the calcaneocuboid joints.
The ankle joint aids with dorsiflexion and plantar flexion of the foot.
Plantar flexion is the movement produced by the muscles in the posterior compartment of the leg. This is the movement that increases the 90 degree angle between the foot and the shin.
Dorsiflexion is produced by the muscles in the anterior compartment of the leg. This is the opposite motion from plantar flexion. Here, the top of the foot is moved towards the tibia.
The three other main joints of the foot, listed below, allow for inversion and eversion of the foot.
The foot is the foundation of movement for the lower part of the body. The muscles of the foot are responsible for the strength required to propel the bones of the feet in a variety of ways. The feet have two types of muscles:
Intrinsic muscles aid with walking and movement of the toes. They also support the arches of the foot.
Extrinsic muscles aid with dorsiflexion and walking. They originate from the three main bones in the leg, the femur, tibia and fibula. The extrinsic muscles of the foot can be broken down into the following three sub categories:
- Extrinsic anterior muscles
- Extrinsic lateral muscles
- Extrinsic posterior muscles
Ligaments are the strong fibrous connective tissues that stabilize joints and bones. In the foot ligaments can be broken down into the following sub categories:
Ligaments Stabilizing Ankle Joint
- Anterior Talo-fibular ligament
- Calcaneo-fibular ligament
- Posterior Talo-fibular ligament
- Deltoid ligament
Ligaments of the Upper Ankle
- Anterior Inferior Tibiofibular ligament
- Interosseous ligament
- Ligament of the Subtalar Joint
- Cervical ligament
Ligaments of the Foot
- Lisfranc ligaments
- Intermetatarsal ligaments
- Joint capsule of great toe