How is bursitis diagnosed?

How is Bursitis Diagnosed?

Bursitis is diagnosed primarily through clinical presentation combined with ultrasonography as the first-line imaging modality, which can confirm bursal distension, characterize fluid content, and guide therapeutic interventions. 1

Clinical Assessment

The diagnosis begins with identifying key clinical features:

• Location-specific pain patterns: Superficial bursitis most commonly affects the olecranon (elbow) and prepatellar (knee) bursae, with less frequent involvement of infrapatellar and calcaneal bursae 2
• Mechanism of injury: Chronic microtrauma (e.g., repetitive kneeling) is the most common cause, though acute trauma, inflammatory arthropathies (gout, rheumatoid arthritis), and infection must be considered 2
• Range of motion assessment: Painful forearm pronation and supination suggests bicipitoradial bursitis 3; hip pain with inguinal mass suggests iliopsoas bursitis 4
• Signs of infection: Fever, warmth, erythema, and acute tenderness raise concern for septic bursitis requiring immediate aspiration 2

Imaging Strategy

Ultrasonography (First-Line)

Ultrasound should be the initial imaging modality for suspected bursitis 1, 5. It provides:

• Direct visualization of bursal distension with fluid or synovial hypertrophy 1
• Differentiation from cellulitis, which can mimic bursitis clinically 2
• Characterization of fluid content (simple fluid vs. complex synovial debris) 6
• Power Doppler assessment of active inflammation 6
• Real-time dynamic evaluation and guidance for therapeutic aspiration or injection 1, 6

For subacromial bursitis specifically, ultrasound demonstrates 76.3% sensitivity, 82.9% specificity, and 78.4% overall diagnostic accuracy when compared to MRI 5. The high positive predictive value (91%) supports its use as an initial diagnostic tool 5.

When to Advance Imaging

MRI should be reserved for:

• Equivocal ultrasound findings with persistent clinical suspicion 5
• Evaluation of associated pathology (rotator cuff tears, labral lesions) 1, 7
• Iliopsoas bursitis requiring differentiation from inguinal masses (lymphadenopathy, hernias, tumors) 4

The ACR Appropriateness Criteria note that calcific tendinitis and chronic bursitis evaluation are covered under chronic shoulder pain protocols 7.

Diagnostic Aspiration

Bursal aspiration is mandatory when infection is suspected 2. Aspirated fluid should undergo:

• Gram stain and culture
• Crystal analysis (to identify gout or calcium pyrophosphate deposition) 3
• Glucose measurement
• Cell count with differential 2

Critical Caveat

Avoid aspiration of chronic microtraumatic bursitis due to risk of iatrogenic septic bursitis 2. Aspiration is appropriate for acute traumatic/hemorrhagic bursitis or when infection cannot be excluded clinically.

Laboratory Testing

Blood work has limited diagnostic utility but can support clinical decision-making:

• White blood cell count and inflammatory markers (ESR, CRP) help distinguish infectious from noninfectious causes 2
• These are adjunctive; they do not replace clinical assessment and imaging

Location-Specific Considerations

• Hip bursitis (trochanteric, iliopsoas): Ultrasound anterior longitudinal scan parallel to femoral neck is most valuable 1; MRI may be needed to exclude hip joint pathology 4
• Elbow bursitis (olecranon, bicipitoradial): Ultrasound shows bursal distension in proximal forearm for bicipitoradial involvement 6, 3
• Shoulder bursitis (subacromial): Ultrasound has good accuracy but MRI remains gold standard for comprehensive soft tissue assessment 5

Common Pitfalls

• Mistaking cellulitis for superficial bursitis: Ultrasound definitively distinguishes these conditions 2
• Assuming all bursitis is infectious: Most cases are microtraumatic or inflammatory; reserve antibiotics for confirmed septic bursitis 2
• Over-reliance on physical examination alone: Clinical diagnosis of bursitis can be difficult, particularly for deep bursae (iliopsoas, bicipitoradial) where imaging is essential 4, 3
• Unnecessary aspiration: Aspirating chronic microtraumatic bursitis increases infection risk without therapeutic benefit 2