Navicular bursitis
The navicular bursa is a small fluid-filled structure in the foot that acts as a cushion where the deep digital flexor tendon passes over the bone and changes direction. A bursa has many properties similar to a joint or a tendon sheath. Bursae are lined with a membrane which produces synovial fluid. Other common bursae in the horse include the calcaneal bursa at the point of the hock, the bicipital bursa over the point of the shoulder, and the supraspinous bursa over the top of the withers.
A radiographic contrast study of the navicular bursa
©Rossdale and Partners Diagnostic Centre