When is magnetic resonance imaging (MRI) indicated for olecranon (elbow) bursitis?

MRI Indications for Olecranon Bursitis

MRI is not routinely indicated for olecranon bursitis, as radiographs are the appropriate initial imaging study to exclude fractures and detect calcifications; MRI should be reserved only for cases where clinical suspicion of septic bursitis remains high despite negative bursal aspiration, or when evaluating for associated soft tissue complications that cannot be assessed by ultrasound. 1

Initial Imaging Approach

• Plain radiographs are the first-line imaging modality for all patients with suspected olecranon bursitis, according to the American College of Radiology. 1
• Radiographs can detect fractures, dislocations, heterotopic ossification, and soft tissue calcifications that may be associated with olecranon bursitis. 1
• Olecranon spurs and amorphous calcium deposits are present in approximately 57% of patients with traumatic olecranon bursitis compared to 14% of controls. 2

Role of Ultrasound

• Ultrasound is the preferred advanced imaging modality for demonstrating bursal thickening, heterogeneous echogenicity in chronic cases, and guiding aspiration. 1
• Ultrasound can effectively differentiate bursitis from cellulitis, which is a critical clinical distinction. 3
• Ultrasound-guided aspiration is safer and more accurate than blind aspiration when infection is suspected. 3

When MRI May Be Considered

Diagnostic Uncertainty After Aspiration

• MRI can help differentiate septic from nonseptic bursitis when bursal aspiration results are equivocal or unavailable. 4
• However, MRI findings show considerable overlap between septic and nonseptic olecranon bursitis without statistically significant differences. 4
• Septic bursitis can be excluded only if both bursal rim enhancement and soft-tissue enhancement are absent on contrast-enhanced MRI. 4

Associated Soft Tissue Complications

• MRI is useful when evaluating for complications such as triceps tendon pathology, bone marrow edema, or deep soft tissue abscesses. 4
• Bone marrow edema is present in 29% of septic cases versus 5% of nonseptic cases, though this difference is not statistically significant. 4
• Moderate to marked soft tissue edema occurs in 64% of septic cases versus 33% of nonseptic cases. 4

MRI Findings (When Performed)

Common Features in Both Septic and Nonseptic Bursitis

• Marginal lobulation: 79% septic versus 48% nonseptic. 4
• Bursa septation: 64% septic versus 57% nonseptic. 4
• Poorly defined margins: 64% septic versus 67% nonseptic. 4
• Elbow joint effusion: 86% septic versus 52% nonseptic. 4

Enhancement Patterns

• Rim enhancement is present in 100% of septic cases with contrast versus 75% of nonseptic cases. 4
• Soft tissue enhancement occurs in 100% of septic cases versus 63% of nonseptic cases. 4

Imaging Modalities NOT Recommended

• CT, bone scan, and contrast-enhanced studies have no established role in the routine evaluation of olecranon bursitis. 1
• The American College of Radiology explicitly advises against routine use of these modalities for bursal pathology. 1

Clinical Algorithm

1. Obtain plain radiographs first in all cases to exclude bony abnormalities and detect calcifications. 1
2. Perform bursal aspiration with fluid analysis (Gram stain, culture, cell count, glucose, crystal analysis) if infection is suspected based on fever >37.8°C, prebursal temperature difference >2.2°C, or skin lesions. 5, 3
3. Use ultrasound to guide aspiration, assess bursal characteristics, and differentiate from cellulitis. 1, 3
4. Reserve MRI for cases with persistent diagnostic uncertainty after aspiration, suspected deep soft tissue complications, or evaluation of associated triceps tendon or bone pathology. 4

Common Pitfalls to Avoid

• Do not order MRI as a first-line test for olecranon bursitis, as it provides no advantage over clinical assessment and bursal aspiration for distinguishing septic from nonseptic disease. 4
• Do not rely on MRI findings alone to diagnose septic bursitis, as there is substantial overlap with nonseptic cases. 4
• Do not perform bursal aspiration for chronic microtraumatic bursitis without clinical suspicion of infection, as this increases the risk of iatrogenic septic bursitis. 3
• Do not assume all cases require advanced imaging, as most olecranon bursitis is managed conservatively based on clinical presentation and radiographs alone. 1, 6, 5