Subscapular Bursa

The subscapular bursa is a synovial fluid-filled sac located between the subscapularis tendon and the neck of the scapulaglenohumeral joint.

Location

The subscapular bursa is situated in the anterior part of the shoulder joint, deep to the subscapularis muscle and superficial to the anterior joint capsule. It lies just medial to the lesser tubercle of the humerus and is positioned anterior to the glenoid cavity and the head of the humerus.

Structure

• Small, flattened, synovial sac lined with a single layer of synoviocytes.
• May appear as a slit-like space in healthy individuals, expanding when inflamed or when fluid accumulates.
• Often communicates with the glenohumeral joint cavity through a small natural opening in the anterior joint capsule.

Function

• Reduces friction: Separates the subscapularis tendon from the neck of the scapula and the joint capsule, facilitating smooth gliding during internal rotation.
• Protects soft tissues: Acts as a buffer between the subscapularis and anterior glenohumeral structures.
• Lubricates movement: Helps maintain joint fluid balance and synovial lubrication in movements involving the anterior shoulder.

Physiological Role(s)

• Prevents mechanical irritation of the subscapularis tendon during repetitive motion.
• Supports functional integrity of the glenohumeral joint by decreasing stress at the tendon-bone interface.
• Plays a role in shoulder joint homeostasis through its communication with the joint cavity.

Relations

• Anterior: Subscapularis muscle and fascia.
• Posterior: Anterior joint capsule and humeral head.
• Medial: Glenoid neck and scapular fossa.
• Lateral: Lesser tubercle of the humerus.

Development

The subscapular bursa forms as a synovial outpouching of the anterior glenohumeral joint capsule during fetal development. In many individuals, this connection persists into adulthood, resulting in an open communication between the bursa and joint space. The size and shape of the bursa are influenced by muscle development, joint mobility, and mechanical loading throughout growth.

Clinical Significance

• Bursitis: Inflammation of the subscapular bursa can lead to anterior shoulder pain, especially during internal rotation or resisted flexion.
• Synovitis: Because the bursa communicates with the joint cavity, inflammatory joint conditions such as rheumatoid arthritis may involve the subscapular bursa.
• Effusion tracking: Joint effusion may extend into the subscapular bursa, making it a useful window for imaging joint inflammation.
• Shoulder instability or surgery: The anterior capsule and subscapular bursa are often involved in arthroscopic approaches or repairs for dislocation.

Imaging

• Ultrasound: Can detect bursal fluid or thickening anterior to the shoulder joint, especially when enlarged or inflamed.
• MRI: Offers the best visualization of the bursa and its communication with the joint, useful in detecting bursitis or capsular defects.
• MR arthrography: Confirms communication between the bursa and the joint cavity and helps evaluate labral or capsular pathology.

Surgical Relevance

• Anterior capsulotomy: The bursa is encountered and preserved or opened during surgeries involving the anterior capsule.
• Arthroscopy portal: The subscapular bursa may serve as a landmark or entry path for anterior arthroscopic portals.
• Injection site: Less commonly targeted directly, but may receive medication when the glenohumeral joint is injected.

Anatomical Variations

• The size, shape, and extent of communication with the glenohumeral joint vary between individuals.
• In some people, the bursa remains isolated from the joint cavity, particularly in early life.
• Occasionally duplicated or partially divided by fibrous septa.