The skeleton of the foot consists of 26 bones and can be grouped into three groups:
- The tarsus (ankle joint).
- The metatarsal.
- The phalanges (bones of the fingers).
There are 7 tarsal bones, 5 metatarsal bones, and 14 phalanges.
Anatomically, the foot can be divided into the forefoot (metatarsals and phalanges), the midfoot (cuboid, navicular, and cuneiform), and the rear foot (calcaneus and talus).
The lesions in the bones of the foot commonly occur in athletes and active individuals. Most injuries are the result of acute trauma during sports.
Adolescents are more vulnerable to these injuries due to incomplete endochondral ossification and the existence of their epiphyseal cartilaginous plates.
As such, it is important to have a basic anatomical understanding regarding the leg bones, including their joints and attachment sites.
The tarsus consists of 7 bones that make up the posterior aspect of the foot: talus, calcaneus, cuboid, navicular, and three cuneiforms. The tarsal bones can be divided into the back of the foot (talus and calcaneus) and the middle of the foot (cuboid and cuneiform).
The navicular is the intermediate bone between these two groups.
The talus (Latin for ankle) is the uppermost bone of the tarsus and rests on the calcaneus. Three areas of articulation make up the ankle joint:
- The superomedial aspect of the talus articulates with the medial malleolus of the tibia
- The superior aspect of the talus articulates with the distal tibia.
- The lateral aspect of the talus articulates with the lateral malleolus of the fibula.
Anteriorly, the talus articulates with the navicular bone. Medially, the talus articulates with the medial talus bone.
The talus has a body, head, and neck. The upper surface, known as the trochlea, has two malleoli attached to it that help with joint stability. The trochlea is wider anteriorly, leading to a difference in stability depending on the position of the joint.
Joint dorsiflexion stretches the ligaments resulting in joint stability. Plantar flexion reduces the width of the trochlea resulting in decreased stability.
The calcaneus is often called the heel bone and is the largest and strongest bone in the foot. The weight of the body passes through the tibia, towards the talus and then towards the calcaneus.
The sustainability tali is a bony prominence on the medial aspect of the calcaneus that supports the medial aspect of the talus bone.
The superior aspect of the calcaneus has three articular surfaces for articulation with the talus. The anterior surface articulates with the cuboid. The posterior aspect of the calcaneus has a large weight-bearing region called the calcaneal tubercle.
A hard fall on the heel (eg, falling off a ladder) can lead to a calcaneal fracture. Diagnosis is based on symptoms (pain, bruising, difficulty walking) and can then be confirmed by X-ray or CT scan.
The cuboid bone articulates posteriorly with the end of the calcaneus. It is the most lateral bone in the distal row of the tarsal bones.
Anterior to the cuboid tuberosity, there is a groove on the lateral and inferior surfaces of the bone that provides a passage for a muscular tendon.
The name of the navicular bone is derived from its resemblance to a small boat. The navicular is located between the head of the posterior talus and the three cuneiforms anteriorly.
The navicular bone is located on the medial aspect of the foot and articulates with the proximal talus, the three cuneiforms distally, and the cuboid laterally.
Cuneiform bones are wedge-shaped. They are called medial, intermediate, and lateral based on their relative position. Each cuneiform has a narrow bottom surface and a wide top surface that results in the transverse curvature of the foot.
Each cuneiform articulates with the posterior navicular and its respective metatarsal anteriorly.
The anterior portion of the foot is made up of the 5 metatarsal bones that are numbered from 1 to 5 starting from the medial aspect of the foot. The first metatarsal is shorter and thicker than the others.
Each metatarsal has a base (proximal), a shaft, and a head (distally). The base of the metatarsal articulates with the cuneiform or cuboid bones. The head of a metatarsal articulates with the proximal phalanges to form the metatarsophalangeal joint (MTP).
The metatarsal heads are in contact with the ground that forms the ball of the foot. The bases of the 5th metatarsals have a large tuberosity that provides an area for tendon attachment.
Metatarsal fractures often occur when a heavy object falls on the foot. These fractures are common in soccer players, either as a result of direct trauma or as stress fractures (“gait fractures”).
Finally, there are 14 phalanges in the foot that are arranged similarly to the hand. The first digit has two phalanges (proximal and distal) while the remaining four digits have three phalanges (proximal, intermediate, and distal).
Like the metatarsals, each phalanx has a base (proximally), an axis, and a head (distally). Like the first metatarsal, the first phalanges of the first digit are short and wide.