The sustentaculum tali is a shelf-like projection on the calcaneus, commonly known as the heel bone. This bony extension plays a role in the complex mechanics of the foot. It contributes to overall foot support and stability, influencing how we stand, walk, and run. It is important for the foot’s load-bearing capabilities.
Anatomical Location and Structure
The sustentaculum tali is located on the medial, or inner, side of the calcaneus. It projects horizontally from the anteromedial portion of the heel bone, positioned just below the medial malleolus, which is the bony prominence on the inside of the ankle. Its shelf-like appearance is a key characteristic.
Its superior surface is concave and forms an articulation with the middle calcaneal surface of the talus, a bone situated directly above it. The sustentaculum tali is composed of robust cortical bone, contributing to its strength.
Key Functions and Role in Foot Stability
A primary function of the sustentaculum tali is to provide support for the talus bone. The talus sits directly on this shelf, forming a significant part of the subtalar joint, which is involved in foot movements. This support is important for distributing body weight effectively across the foot.
The sustentaculum tali also participates in weight bearing during activities such as standing, walking, and running. It helps transfer forces from the leg to the foot, contributing to efficient locomotion.
It contributes indirectly to maintaining the medial longitudinal arch of the foot. By supporting the talus, it provides a stable foundation for the ligaments and tendons that uphold this important arch. The sustentaculum tali also acts as a trochlea, or pulley system, for specific tendons, changing their direction and enhancing their mechanical advantage during movement.
Associated Ligaments and Tendons
The sustentaculum tali serves as an attachment point and guiding structure for several soft tissues. A portion of the deltoid ligament attaches to its medial surface. This attachment contributes to stabilizing the ankle joint on its inner side.
The spring ligament, also known as the plantar calcaneonavicular ligament, originates from the anterior surface of the sustentaculum tali. This ligament supports the head of the talus and contributes to maintaining the medial longitudinal arch of the foot.
The tibialis posterior tendon passes inferior to the sustentaculum tali, utilizing it as a pulley to change its direction of pull. This interaction is important for foot inversion, which is the movement of turning the sole of the foot inward. The flexor hallucis longus tendon, responsible for flexing the great toe, also runs along a groove on the inferior surface of the sustentaculum tali.
Common Injuries and Conditions
Fractures involving the sustentaculum tali are uncommon in isolation due to its robust cortical bone structure. However, it can be involved in more extensive calcaneal fractures. Such involvement can lead to pain, deformity, and impaired foot function.
Stress fractures of the sustentaculum tali occur in athletes or individuals exposed to repetitive stress on the foot. Damage to the sustentaculum tali can also impact the subtalar joint, resulting in instability or chronic pain in the hindfoot.
Inflammation of the tendons that pass around the sustentaculum tali, such as tibialis posterior tendonitis, can cause pain in this region. This pain is sometimes mistakenly attributed directly to the bone itself. Pain in this area is often linked to overuse or biomechanical issues affecting the structures the sustentaculum tali supports or interacts with.