The bones of the foot provide mechanical support for the soft tissues, helping the foot withstand the weight of the body both while standing and in motion. They can be divided into three groups - Tarsals, Metatarsals, and Phalanges. The Tarsals consist of seven irregularly shaped bones located in the ankle area proximally in the foot. The Metatarsals connect the Phalanges to the Tarsals, and there are five Metatarsals, one for each digit. The Phalanges are the bones of the toes, each toe having three Phalanges - proximal, intermediate, and distal, with the exception of the big toe, which only has two Phalanges. Additionally, the foot can also be divided into three sections - the Hindfoot, Midfoot, and Forefoot.
The Hindfoot consists of the talus and the calcaneus and forms the bony framework around the proximal ankle and heel. The Talus is the most superior of the Tarsal bones and transmits the weight of the entire body to the foot, having three articulations - Superiorly to the ankle joint, between the Talus and the bones of the leg (the tibia and fibula); Inferiorly to the subtalar joint, between the Talus and the Calcaneus; and Anteriorly to the talonavicular joint, between the Talus and the Navicular. The Calcaneus is the largest tarsal bone, lying underneath the Talus and constituting the heel. It has two articulations- Superiorly to the subtalar joint, between the Calcaneus and the Talus; and Anteriorly to the calcaneocuboid joint, between the Calcaneus and the Cuboid. It protrudes posteriorly and takes the weight of the body when the heel hits the ground while walking. The posterior aspect of the Calcaneus is marked by a calcaneal tuberosity, to which the Achilles tendon attaches.
The intermediate row of Tarsal bones contains one bone, the Navicular, which is shaped like a boat and is positioned medially. It articulates with the Talus posteriorly, the three Cuneiform bones anteriorly, and the Cuboid laterally. There is a tuberosity on the plantar surface of the Navicular, to which part of the tibialis posterior tendon attaches. The distal row of Tarsal bones consists of four bones - the Cuboid and the three Cuneiforms. These bones articulate with the Metatarsals of the foot.
The Cuboid is furthest lateral, lying anterior to the Calcaneus and behind the fourth and fifth Metatarsals. It is cuboiidal in shape and the inferior surface is marked by a groove for the tendon of fibularis longus. The three Cuneiforms (lateral, intermediate (or middle) and medial) are wedge shaped bones. They articulate with the Navicular posteriorly, and the Metatarsals anteriorly, and their shape helps form a transverse arch across the foot.
The anatomy of the bones of the foot is incredibly important in terms of providing mechanical support for the soft tissues, enabling the foot to bear the weight of the body. This article has explored the bony landmarks, articulations, and clinical correlations of the Tarsals, Metatarsals, and Phalanges, as well as providing an understanding of how the foot can be divided into sections.
The talus, the largest of the tarsal bones, has three articulations: superiorly with the ankle joint between the talus and the bones of the leg (tibia and fibula); inferiorly with the subtalar joint between the talus and calcaneus; and anteriorly with the talonavicular joint between the talus and the navicular. This bone is responsible for transmitting forces from the tibia to the calcaneus (heel bone). The calcaneus is the largest of the tarsal bones and lies inferior to the talus. It articulates superiorly with the subtalar joint between the calcaneus and the talus, and anteriorly with the calcaneocuboid joint between the calcaneus and the cuboid. The posterior projection of the calcaneus carries the main weight of the body as the heel hits the ground when walking.
The intermediate row of tarsal bones contains one bone, the navicular, which articulates posteriorly with the talus, anteriorly with all three cuneiform bones, and laterally with the cuboid bone. The distal row of tarsal bones is composed of four bones – the cuboid, and the three cuneiforms. These bones articulate with the metatarsals of the foot. The cuboid is the furthest lateral, lying anterior to the calcaneus and behind the fourth and fifth metatarsals. The three cuneiforms (lateral, intermediate (or middle) and medial) are wedge-shaped bones. They articulate posteriorly with the navicular, and anteriorly with the metatarsals. The shape of the bones helps form a transverse arch across the foot.
The talus and calcaneus bones, located in the proximal part of the foot and ankle, are involved in transmitting forces from the body to the ground. Hence, they are the most frequently fractured of all the tarsal bones. Talar fractures most commonly occur in the neck of the talus (50%), but can occur in the talar body or lateral process as well. Fractures in the talar head are less likely. Neck fractures usually result from high energy injuries, due to excessive dorsiflexion of the foot pushing the neck of the talus against the tibia. Such fractures may disturb the blood supply to the talus, leading to avascular necrosis of the bone. On the other hand, body fractures are usually caused by jumping from a height. As for calcaneal fractures, they typically occur from axial loading – mainly from a fall from a height. The bone can fracture into multiple pieces (comminuted fracture). X-ray will show the calcaneus shorter and wider. Even after medical treatment, this kind of fracture can cause further issues. The subtalar joint is usually disrupted, leading to arthritic pain upon inversion and eversion. The calcaneo-cuboid joint can also be affected.
The metatarsals are located in the forefoot, between the tarsal and phalangeal bones. They are numbered I-V (medial to lateral). Each metatarsal is similar in structure, convex dorsally and consisting of a head, neck, shaft, and base (distal to proximal). There are three or four articulations associated with the metatarsals: proximally, tarsometatarsal joints between the metatarsal bases and the tarsal bones; laterally, intermetatarsal joints between the metatarsal and the adjacent metatarsals; and distally, metatarsophalangeal joints between the metatarsal head and the proximal phalanx.
Metatarsal fractures can result from a variety of causes. The most common method of fracture is a direct blow to the foot, usually from a heavy object dropping onto the foot. Another type of metatarsal injury is known as a stress fracture, an incomplete fracture caused by repeated stress to the bone. It is common in athletes and occurs most frequently at the necks of the second and third metatarsals and the proximal fifth metatarsal. Excessive inversion of the foot can also cause the fibularis brevis muscle to avulse the base of the fifth metatarsal, resulting in a fracture.
The phalanges are the bones of the toes. The second to fifth toes all have proximal, middle, and distal phalanges, while the great toe only has proximal and distal phalanges. They are similar in structure to the metatarsals, each phalanx consisting of a base, shaft, and head.
