Shoulder bursitis is inflammation of the subacromial bursa — a fluid-filled sac that cushions the rotator cuff tendons as they glide beneath the acromion. When the bursa becomes irritated and inflamed, it swells with excess fluid, causing pain and restricted shoulder movement.
Shoulder bursitis rarely occurs in isolation. It is almost universally associated with subacromial impingement syndrome, sharing the same mechanical basis of a narrowed subacromial space. Chronic bursal inflammation is a major contributor to progressive rotator cuff tendon damage, and in some patients, calcific deposits within the rotator cuff — calcific tendinitis — are the primary trigger of acute, severe bursitis. When bursitis develops after a traumatic event, imaging should also evaluate for an underlying rotator cuff tear that may be driving the inflammatory response.
Causes
Repetitive overhead activity.
Repeated compression of the subacromial bursa during overhead lifting, throwing, or reaching is the most common cause. This is frequently associated with subacromial impingement syndrome, as the two conditions often coexist and share the same mechanical basis — a curved or hooked acromion, acromioclavicular joint spurring, or poor rotator cuff muscle balance all reduce the space available for the bursa and underlying tendons.
Direct trauma and other causes.
A fall or direct blow to the shoulder can acutely inflame the bursa. Bursitis can also develop as a complication of rotator cuff tears, adjacent calcific tendinitis, rheumatoid arthritis, gout, or infection (septic bursitis). Calcium deposits from calcific tendinitis can rupture directly into the bursa, triggering a sudden, intensely painful episode of acute bursitis that may be the presenting complaint even when underlying tendon pathology has been present for some time. In some cases, bursitis develops without a clear precipitating cause.
Symptoms
The primary symptom is pain at the outer aspect of the shoulder that worsens with overhead motion and pressure on the shoulder, such as lying on the affected side at night. Night pain is a particularly common and disruptive feature of subacromial bursitis. The shoulder may feel swollen or warm to the touch in acute cases, and a painful arc during arm elevation between 60 and 120 degrees is characteristic. As the condition becomes chronic, stiffness and loss of range of motion may develop, with some patients progressing toward adhesive capsulitis (frozen shoulder) if pain leads to prolonged guarding and immobility. In septic bursitis, symptoms are typically more severe and accompanied by fever, significant warmth, and erythema requiring urgent evaluation.
Diagnosis
A physical exam by a doctor typically reveals tenderness over the lateral shoulder, a painful arc of motion, and positive impingement signs including the Hawkins-Kennedy and Neer tests. A subacromial bursa injection of local anesthetic that produces immediate pain relief strongly supports the diagnosis. An MRI is used to confirm bursal inflammation — identified by fluid signal and thickening within the subacromial-subdeltoid bursa — and to evaluate the rotator cuff tendons for associated partial or full-thickness tears, calcific deposits, and acromial morphology contributing to the problem. This comprehensive tissue assessment is the key advantage of MRI over ultrasound, which can detect bursal fluid but cannot fully characterize the deeper tendon and bone architecture that determines whether conservative or surgical treatment is appropriate.
Bursitis classification
Doctors classify shoulder bursitis based on the cause and duration of symptoms.
- Acute bursitis: Sudden onset of severe pain, often following a specific activity, minor trauma, or calcium crystal rupture into the bursa. The bursa is acutely distended with fluid and the patient may have difficulty moving the arm at all.
- Chronic bursitis: Persistent, lower-grade pain resulting from repeated episodes of inflammation or longstanding mechanical irritation. The bursa wall becomes thickened and fibrotic over time, reducing its capacity to cushion the underlying tendons.
- Septic bursitis: Bacterial infection of the bursa, most commonly caused by Staphylococcus aureus. Presents with intense pain, redness, warmth, and systemic signs of infection. Requires prompt aspiration, culture, and antibiotic treatment to prevent spread to adjacent joint structures.
Treatments
Treatment depends on the type of bursitis, severity of symptoms, and any underlying contributing conditions.
After initial onset of symptoms, rest, ice, activity modification, and anti-inflammatory medications are recommended to reduce acute inflammation.
Acute and chronic bursitis: Physical therapy to address underlying muscular imbalances, scapular mechanics, and rotator cuff strength — the same factors that drive impingement syndrome — forms the foundation of conservative management. Corticosteroid injection directly into the subacromial bursa provides highly effective relief for most patients, reducing inflammation rapidly and allowing more productive participation in rehabilitation. Most patients respond well to one to two injections combined with a structured physical therapy program.
Persistent chronic bursitis not responding to conservative care
Arthroscopic bursectomy — removal of the inflamed and thickened bursa — is reserved for chronic cases that do not respond to prolonged conservative management. This is typically combined with subacromial decompression (acromioplasty) and any necessary rotator cuff repair at the time of surgery, since bursitis at this stage is almost always accompanied by tendon pathology. After surgery, a thorough physical therapy program is critical to restoring strength and range of motion.
Septic bursitis
Septic bursitis requires aspiration of the infected fluid for culture and sensitivity testing, followed by a course of appropriate antibiotics targeted to the identified organism. Surgical drainage may be necessary in severe, rapidly progressive, or antibiotic-refractory cases. Prompt treatment is essential to prevent spread of infection to the glenohumeral joint, which would constitute a surgical emergency.
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