The sinus tarsi is an anatomical space within the foot. Its function is important for foot health and mobility, and understanding it helps shed light on certain types of foot pain and instability.
Anatomical Location of the Sinus Tarsi
The sinus tarsi is a tunnel or canal found on the lateral (outer) side of the foot, positioned between the talus (ankle bone) and the calcaneus (heel bone). It divides the subtalar joint into anterior and posterior compartments.
Within this space, structures are housed, contributing to the foot’s mechanics. These include a network of ligaments, such as the interosseous talocalcaneal ligament and the cervical ligament, alongside roots of the inferior extensor retinaculum. The sinus tarsi also contains adipose (fat) tissue, blood vessels, and nerve endings. These elements contribute to stability and sensation in the foot.
Role in Foot Movement and Stability
The structures within the sinus tarsi play a role in the biomechanics of the foot, particularly in stabilizing the subtalar joint. Ligaments like the interosseous talocalcaneal ligament and the cervical ligament limit excessive movement, such as inversion or eversion. This controlled stability helps maintain balance and proper foot alignment during various activities.
Beyond mechanical support, the sinus tarsi is rich in proprioceptive nerve endings. These nerve endings provide the brain with information about the foot’s position and movement in space. This feedback helps coordinate foot movements, adapt to uneven surfaces, and maintain balance while walking or running.
Common Issues Affecting the Sinus Tarsi
The sinus tarsi can become a source of pain, most commonly associated with Sinus Tarsi Syndrome. This syndrome arises after a traumatic ankle injury, especially an inversion ankle sprain. Repetitive stress or overuse, such as from prolonged standing or walking, can also contribute to its development.
Symptoms of Sinus Tarsi Syndrome include pain and tenderness on the outer side of the ankle, specifically in the hollow area between the ankle and heel bones. This pain may worsen with activity, particularly when walking on uneven ground, or with movements that involve turning the foot inward or outward. Individuals may also experience a feeling of instability in the hindfoot. The condition can also be linked to foot deformities like flat feet, where compression in the sinus tarsi space can lead to irritation and inflammation.