The tarsal bones are a collection of seven bones located in the ankle and upper foot, forming the tarsus. This complex foundation connects the bones of the lower leg to the long bones of the midfoot. The tarsal bones are classified as short bones in the human skeleton, distinguishing them from long bones, like the femur, or flat bones, such as the scapula.
Classification as Short Bones
Short bones are defined by their shape, which is roughly cube-like, meaning their length, width, and thickness are all nearly equal. This dense, compact structure is different from the elongated shaft and flared ends of long bones, which are designed for large movements and leverage. The interior of a short bone consists primarily of spongy or cancellous bone tissue, which is covered by a thin shell of compact bone.
This morphology, featuring a thin layer of compact bone around a spongy core, makes short bones well-suited for providing stability and support in the joint. Short bones, including the tarsals and the carpal bones of the wrist, permit limited, controlled movements between their numerous articulating surfaces. Unlike long bones that act as levers, short bones contribute to the overall strength and structural integrity of a complex joint system. They are designed to absorb and distribute mechanical stress across multiple small points of articulation.
Location and Function in the Foot
The tarsal bones are located in the posterior aspect of the foot, collectively forming the hindfoot and midfoot regions. They serve as the anatomical bridge between the lower leg bones—the tibia and fibula—and the five metatarsal bones leading to the toes. This location is important, as the tarsus must absorb and transmit the entire body’s weight from the leg to the ground.
The arrangement of these seven bones acts as a natural shock absorber during standing, walking, and running. Their collective structure forms the two major arches of the foot: the longitudinal arch and the transverse arch. These arches allow for a spring-like action that dampens impact and converts the force of a step into forward motion. The complex joints between the tarsal bones permit the foot to adapt to uneven terrain while maintaining balance and stability.
The Seven Tarsal Bones
The largest tarsal bone is the calcaneus, commonly known as the heel bone. It forms the prominent posterior point of the foot and bears the majority of the weight during walking. Sitting superior to the calcaneus is the talus, which is the only bone that articulates directly with the tibia and fibula to form the ankle joint.
Distal to the calcaneus and talus are the remaining five bones:
- The navicular is a boat-shaped bone located on the medial side of the foot.
- The cuboid is situated on the lateral side, connecting to the fourth and fifth metatarsals.
- The three cuneiforms are wedge-shaped bones named for their position: medial, intermediate, and lateral.
These three cuneiforms articulate with the navicular posteriorly and the first three metatarsals anteriorly, completing the rigid midfoot structure.