Clinical Presentation of Subacromial Bursitis
Subacromial bursitis presents with anterior or anterolateral shoulder pain that worsens with overhead activities, accompanied by decreased range of motion particularly during abduction, and positive impingement signs on physical examination. 1
Primary Pain Characteristics
- Pain location: Anterior or anterolateral aspect of the shoulder with 88% sensitivity for diagnosis 1
- Pain pattern: Worsens specifically with overhead movements and activities requiring arm elevation above shoulder level 2, 1
- Night pain: Common complaint that interferes with sleep, particularly when lying on the affected shoulder 2
- Activity-related pain: In throwing athletes, pain occurs during specific phases including arm cocking and acceleration phases 1
Physical Examination Findings
- Neer's test: Positive in most cases (88% sensitivity, though only 33% specificity) 1
- Hawkins' test: Highly sensitive at 92% (forcible internal rotation with arm flexed forward at 90 degrees), though specificity is only 25% 1
- Range of motion deficits: Decreased active and passive abduction, particularly with external or internal rotation 1
- Focal weakness: Present in approximately 75% of patients with subacromial pathology 1
- Painful arc: Pain during mid-range abduction (60-120 degrees) as the inflamed bursa is compressed beneath the acromion 3
Associated Pathophysiological Signs
- Supraspinatus tendon irritation: Results from subacromial outlet obstruction and compression 1
- Scapular dyskinesis: Poor coordination of scapular movements during arm elevation contributes to ongoing impingement 1
- Rotator cuff weakness: Combined with ligamentous laxity, particularly in younger athletes, creates difficulty maintaining humeral head centering in the glenoid fossa 1
- Muscular imbalance: Weakened posterior shoulder musculature with overdeveloped anterior muscles creates abnormal biomechanics 1
Imaging Findings
- MRI sensitivity: 90% for detecting soft tissue abnormalities in the supraspinatus tendon, subacromial bursa, and biceps tendon (80% specificity) 1
- Ultrasound: Equivalent to MRI for detecting rotator cuff abnormalities with 85% sensitivity and 90% specificity 1
- Bursal thickening: Visible on ultrasound or MRI as fluid or inflammatory changes within the subacromial-subdeltoid bursa 4
Atypical Presentations to Consider
- Massive swelling: Rarely, subacromial bursitis can present as a large mass mimicking a neoplasm, particularly in rheumatoid arthritis patients, though this lacks typical inflammatory signs 5
- Chronic presentation: Symptoms persisting beyond 6 weeks despite conservative measures indicate chronic subacromial bursitis requiring more aggressive intervention 4, 6
Progressive or Untreated Disease Signs
- Decreased throwing velocity: In athletes, progressive decline in performance and precision indicates advancing pathology 1
- Tendon degeneration: Risk of progression to partial or full-thickness rotator cuff tears if left untreated 1
- Functional decline: Increasing difficulty with activities of daily living requiring shoulder elevation 2
Critical Differential Diagnosis Considerations
- Primary versus secondary impingement: Primary is more common in adults due to extra-articular rotator cuff pathology; secondary is more common in younger athletes with rotator cuff weakness and ligamentous laxity 1
- Rotator cuff tears: May present identically but require different management strategies, particularly if full-thickness 7, 1
- Septic bursitis: Consider if fever, redness, or sudden increase in pain and swelling occur, particularly after corticosteroid injection 8
Red Flags Requiring Immediate Evaluation
- Sudden increase in pain or swelling: May indicate infection or acute tear progression 2
- New weakness in the arm: Suggests possible rotator cuff tear requiring urgent imaging 2
- Fever and redness: Indicates possible septic bursitis, including rare methicillin-resistant Staphylococcus aureus infection after injection 8