The talus bone, or ankle bone, is a component of the human foot, nestled within the ankle joint. It connects the lower leg to the foot, managing forces during daily activities.
Anatomical Position
The talus is situated in the hindfoot. It is the second largest of the seven tarsal bones, with only the calcaneus (heel bone) being larger. The talus articulates with four other bones: the tibia, fibula, calcaneus, and navicular.
Superiorly, the talus forms the talocrural joint by articulating with the distal ends of the tibia (shin bone) and fibula (calf bone). Its curved upper surface, called the talar dome, fits into the mortise created by these lower leg bones. Inferiorly, the talus connects with the calcaneus to form the subtalar joint, which permits side-to-side motion of the foot. Anteriorly, its head articulates with the navicular bone, contributing to the talocalcaneonavicular joint. The talus is largely covered by articular cartilage, a smooth tissue that facilitates fluid movement against adjacent bones.
Essential Function
The talus transmits body weight and forces from the lower legs to the foot. Its weight-bearing capacity supports upright posture and locomotion. The bone’s saddle-like shape and extensive cartilage covering allow for efficient pressure distribution across the ankle joint.
It enables ankle movement, specifically dorsiflexion (moving the foot upwards) and plantarflexion (moving the foot downwards). Through its articulation with the calcaneus, the talus also facilitates inversion (turning the sole inward) and eversion (turning the sole outward) of the foot. These movements are important for adapting to uneven terrain and maintaining balance. The talus also contributes to shock absorption during activities like walking, running, and jumping.
Common Issues
Due to its role in weight-bearing and its blood supply, the talus is susceptible to specific injuries. Fractures often result from high-energy trauma, such as car accidents or falls. The most common site for a talus fracture is its neck, located between the body and the head. These fractures are problematic because the talus has limited muscular attachments and a delicate blood supply, which can impede healing.
Another common issue is an osteochondral lesion of the talus (OLT), which involves damage to the cartilage and underlying bone on the talar dome. These lesions often occur following traumatic ankle injuries, such as severe sprains, where a portion of the talus impacts other ankle joint structures. Symptoms include localized ankle pain, swelling, and a sensation of catching or locking in the joint.
A complication that can arise, particularly after a talus fracture, is avascular necrosis (AVN). AVN occurs when the blood supply to the talus is interrupted, leading to the death of bone tissue. The talus has a precarious blood supply, making it vulnerable to AVN, especially after severe injuries. Without adequate blood flow, the bone can soften and eventually collapse, leading to severe pain and significant loss of ankle function.