Anatomy, Shoulder and Upper Limb, Hand Ulnar Bursa

Bursae are sac-like structures lined with synovial fluid. They are found in friction-prone locations in the musculoskeletal system, such as bony prominences and areas surrounding tendons and ligaments. They ensure smooth movement by creating a physiologic cushion between adjacent tissues and structures. The term bursae is Latin for "moneybags."

The synovial tendon sheath is a bursa that surrounds tendons as they pass through anatomic spaces. The ulnar bursa is the synovial tendon sheath enclosing the tendons of the medial 4 fingers' flexors as they pass through the carpal tunnel (see Image. Hand Bursae). It possesses 3 distinct invaginations that surround the structures of the carpal tunnel :

1. Deep layer: between the carpal bones and the flexor digitorum profundus tendons

2. Intermediate layer: between the flexor digitorum profundus tendons and flexor digitorum superficialis tendons

3. Superficial layer: superficial to the flexor digitorum superficialis tendons