Subdeltoid

Subdeltoid refers to an anatomical region in the shoulder, defined by a potential space beneath the deltoid muscle. It is most commonly discussed in the context of the subacromial–subdeltoid bursa, a lubricating sac that reduces friction between the deltoid and the underlying rotator cuff tendons and the overlying acromion.

Anatomy and variation: The subdeltoid portion lies lateral to the acromion and overlies the rotator cuff, particularly the supraspinatus tendon. In many individuals the subdeltoid bursa is continuous with the subacromial bursa, forming a single subacromial–subdeltoid bursa; in others they may be delineated as separate spaces with potential communication between them.

Function: The bursa acts as a cushion to minimize friction during shoulder movements such as abduction and overhead motion, allowing smooth interaction between the deltoid muscle, rotator cuff tendons, and the acromion.

Clinical significance: Subdeltoid bursitis is inflammation of this space and can cause lateral shoulder pain, swelling, and restricted range of motion. It may occur with rotator cuff pathology, impingement, or adhesive capsulitis. Diagnosis is supported by clinical assessment and imaging, with ultrasound or MRI identifying bursal distention. Treatments include activity modification, nonsteroidal anti-inflammatory drugs, physical therapy, and corticosteroid injections into the subdeltoid space; refractory cases may require aspiration or surgical intervention.