Bursae of the Shoulder Joint

Several bursae are related to the shoulder joint. Some communicate with the joint cavity and are clinically important.

Subacromial Bursa (Subdeltoid Bursa)

The largest bursa in the body.

Location: Below the coracoacromial arch and deltoid muscle; above the supraspinatus tendon and greater tubercle of the humerus.

The subacromial and subdeltoid bursae are commonly continuous with each other but may be separate. Collectively called the subacromial bursa.

Functions:

Protects the supraspinatus tendon from friction against the acromion
Facilitates movement of the supraspinatus tendon under the coracoacromial arch
During overhead abduction, allows the greater tubercle to pass smoothly under the acromion

Does not communicate with the joint cavity normally.

Location: Between the tendon of subscapularis and the neck of the scapula.

Protects the subscapularis tendon from friction against the scapular neck
Usually communicates with the joint cavity (via an aperture in the anterior capsule below the coracoid process)

Location: Between the tendon of infraspinatus and the posterolateral aspect of the joint capsule.

May communicate with the joint cavity (via an aperture in the posterior capsule)

Bursae that communicate with the synovial cavity mean that opening a bursa may enter the joint
Subacromial bursitis is usually secondary to inflammation of the supraspinatus tendon
Dawbarn’s sign: In subacromial bursitis, pressing below the acromion with the arm adducted causes pain. With the arm abducted, pressure on the same point causes no pain because the bursa disappears under the acromion
Calcium deposition in the supraspinatus tendon irritates the overlying subacromial bursa, causing painful arc syndrome (pain at 60°–120° of abduction)