Subacromial bursitis is a common source of shoulder pain resulting from the inflammation of the subacromial bursa, a small, fluid-filled sac located in the shoulder joint. Bursitis refers to the inflammation of a bursa, which are cushions found near joints throughout the body. Inflammation of the subacromial bursa leads to significant discomfort and restricted movement. This condition is often associated with activities that involve repetitive arm motion, making it a frequent complaint in active individuals and those with physically demanding occupations.
Understanding the Subacromial Bursa
The subacromial bursa is a thin, lubricated sac filled with synovial fluid, situated beneath the acromion, the bony tip of the shoulder blade. This structure acts as a protective cushion between the bone and the rotator cuff tendons. Its function is to reduce friction and allow for smooth, gliding movement as the arm is lifted and rotated.
The subacromial space is narrow, typically measuring only about 1.0 to 1.5 centimeters in height. Swelling of the bursa immediately increases pressure on the adjacent tendons due to this limited space. When the bursa becomes irritated and inflamed, it thickens and produces excess fluid, compromising the smooth mechanics of the shoulder joint. This loss of a smooth interface leads to the pain and restricted motion characteristic of the condition.
Causes and Risk Factors
Subacromial bursitis develops when the bursa is subjected to excessive friction, pressure, or trauma. Causes are separated into acute events, such as a direct impact or sudden injury, and chronic patterns of mechanical stress. An acute cause, like a fall onto an outstretched arm, can lead to immediate swelling and pain.
More commonly, the condition arises from chronic overuse and repetitive overhead activities. Individuals in jobs requiring frequent arm elevation (e.g., painting, carpentry) or athletes in overhead sports (e.g., baseball, swimming) are at higher risk due to constant mechanical strain.
The condition is closely linked to shoulder impingement syndrome, which occurs when the space for the bursa and rotator cuff tendons narrows. Underlying health conditions, including systemic inflammatory diseases like rheumatoid arthritis, gout, and diabetes, can also predispose an individual to bursitis. Poor posture and age-related changes, such as bone spurs, can further reduce the subacromial space, increasing irritation.
Recognizing the Symptoms
The primary sign of subacromial bursitis is pain, typically localized to the anterolateral aspect of the shoulder. This discomfort may be a sharp pain with movement or a dull, persistent ache that can radiate down the arm. The pain is exacerbated by specific motions, particularly lifting the arm above shoulder height or reaching behind the back.
Patients frequently report difficulty sleeping because the pain worsens at night, especially when lying on the affected side. The inflammation leads to a limited range of motion, making simple daily tasks challenging. In more severe cases, the constant pain can lead to functional weakness when attempting to lift or carry objects. Tenderness to the touch may also be present just below the acromion.
Diagnosis and Treatment Options
Diagnosis typically begins with a thorough physical examination and medical history, focusing on the onset and nature of the pain. A healthcare provider tests the shoulder’s active and passive range of motion, often observing pain when the arm is abducted between 70 and 120 degrees. Specific orthopedic impingement tests are performed to reproduce the pain by compressing the inflamed bursa.
While the condition is primarily a clinical diagnosis, imaging tests are often ordered to rule out other causes of shoulder pain. X-rays can identify bone spurs or arthritis that may be contributing to the issue. Ultrasound or Magnetic Resonance Imaging (MRI) may be used to visualize soft tissues, confirming bursa inflammation and assessing the adjacent rotator cuff tendons.
The majority of subacromial bursitis cases respond well to conservative, non-surgical management. Initial treatment focuses on reducing inflammation through rest and avoiding the specific activities that aggravate the shoulder. Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, are commonly used to alleviate pain and swelling.
Physical therapy is a standardized component of recovery, aiming to restore proper shoulder mechanics through targeted stretching and strengthening exercises. For persistent symptoms, a corticosteroid injection directly into the subacromial bursa can provide localized relief from inflammation. Surgery, typically an arthroscopic bursectomy to remove the inflamed tissue, is only considered in rare, chronic cases that have failed to respond to all other non-invasive treatments.