The tarsal bones are seven bones located in the rear and middle of the human foot. They provide the foot’s unique shape, mechanical properties, and structural integrity. Without these specialized bones, the foot would lack the necessary strength and flexibility required for daily activities.
Individual Tarsal Bones
The calcaneus, commonly known as the heel bone, is the largest tarsal bone. Its robust structure bears the majority of the body’s weight during standing and walking. It articulates superiorly with the talus and anteriorly with the cuboid bone.
The talus, located directly above the calcaneus, links the leg and the foot. This bone has no muscle attachments, relying on strong ligaments to hold it in place. It articulates superiorly with the tibia and fibula, forming the ankle joint, and inferiorly with the calcaneus.
The navicular bone, boat-shaped and on the medial side of the foot, is located anterior to the talus. It articulates posteriorly with the talus and anteriorly with the three cuneiform bones. The navicular plays a role in maintaining the medial longitudinal arch of the foot.
The cuboid bone, named for its cube-like appearance, is on the lateral side of the foot, anterior to the calcaneus. It articulates posteriorly with the calcaneus and anteriorly with the fourth and fifth metatarsal bones. The cuboid contributes to the lateral column of the foot.
The three cuneiform bones are wedge-shaped and positioned anterior to the navicular bone. They are designated as medial (first), intermediate (second), and lateral (third) cuneiforms, moving from the inside to the outside of the foot. These bones articulate with the navicular posteriorly and with the first, second, and third metatarsal bones anteriorly, forming part of the transverse arch of the foot.
Role in Foot Function
The tarsal bones form the foot’s arches: the medial and lateral longitudinal arches, and the transverse arch. These arches act as dynamic shock absorbers, distributing forces during movement. This structural design helps protect the bones and joints from excessive stress.
Beyond shock absorption, the tarsal bones enable the foot to adapt to various surfaces and maintain balance. Their numerous articulations allow for complex movements such as inversion, where the sole of the foot turns inward, and eversion, where it turns outward. These motions are essential for navigating uneven terrain and maintaining stability during dynamic activities.
The tarsal bones also play a role in weight bearing, distributing the body’s load from the lower leg through the ankle and across the foot. This distribution is not static; it shifts dynamically during walking and running, allowing the foot to transition from a flexible structure for shock absorption to a rigid lever for propulsion. This dual function is essential for efficient human locomotion.
Common Tarsal Bone Issues
Fractures are common issues affecting tarsal bones, often resulting from high-impact trauma. A calcaneus fracture, for instance, typically occurs from falls from a height, leading to significant pain and impaired weight bearing. Talus fractures can also occur from severe ankle sprains or direct impact, and may disrupt the ankle joint’s smooth function.
Beyond fractures, the joints formed by the tarsal bones are susceptible to sprains, which involve the stretching or tearing of ligaments that connect these bones. Such injuries can lead to instability and discomfort within the midfoot. These sprains can vary in severity, affecting mobility and requiring a period of rest and protection.
Tarsal coalition is a condition where two or more tarsal bones are abnormally connected, either by bone, cartilage, or fibrous tissue, which can restrict normal foot motion. This congenital anomaly can lead to stiffness, pain, and a flatfoot deformity. Another condition, tarsal tunnel syndrome, involves compression of the tibial nerve as it passes through a narrow space on the inside of the ankle, causing pain, numbness, or tingling in the foot.