The subdeltoid bursa is a fluid-filled sac located under the deltoid muscle in the shoulder joint. It plays an important role in decreasing friction in the shoulder joint and protects the surrounding tissues of the joint.
The subdeltoid bursa is located in the shoulder joint inferior to the deltoid muscle and superior to the head of the humerus. It is a thin, flat sac made of fibrous connective tissue lined with synovial membrane. The synovial membrane produces an oily secretion known as synovial fluid that helps to reduce friction within the bursa during movements at the shoulder joint.
The shoulder joint is under an incredible amount of stress due to the many forces that act upon it throughout the typical day. The shoulder must support the entire weight of the arm and whatever the arm moves, while also providing a wide range of motion. The deltoid muscle abducts the arm, which is a common motion performed while lifting heavy objects. As the deltoid muscle contracts superior to the shoulder, it rubs against the head of the humerus and the joint capsule, which would cause irritation to the delicate structures of the joint. The subdeltoid bursa absorbs the shock and friction at the joint to protect the underlying structures.
Frequent movement of the deltoid can cause irritation of the subdeltoid bursa, leading to a painful condition known as bursitis. Bursitis is usually treated by resting the joint, applying ice, and taking non-steroidal anti-inflammatory drugs (NSAIDs) to reduce pain and inflammation of the joint.