Olecranon Bursitis Imaging Signs: Septic vs Non-Septic Elbow Swelling

Septic bursitis is caused by bacterial inoculation through adjacent skin abrasion, puncture wound, or hematogenous spread, most commonly by Staphylococcus aureus. Clinical features favoring septic bursitis include surrounding cellulitis extending beyond the bursa, skin warmth and erythema, fever, and a history of local trauma or skin break. Bursal fluid aspiration and analysis is the definitive diagnostic step: white cell count exceeding 50,000 cells/mm³ with predominant neutrophils, positive Gram stain, or positive culture confirms infection. Non-septic bursitis may follow repetitive friction (student's or miner's elbow), gout, or rheumatoid disease, and fluid is typically less cloudy with lower cell counts and positive crystal analysis in crystal arthropathy.

Aspiration serves both diagnostic and therapeutic purposes. Removing bursal fluid immediately reduces pain and swelling and allows the bursa wall to appose, potentially expediting resolution. Fluid should be sent for culture, sensitivity, Gram stain, cell count and differential, and crystal analysis to guide management. For septic bursitis, aspiration is combined with systemic antibiotics; repeated aspiration or surgical incision and drainage is required if fluid re-accumulates rapidly or the patient fails antibiotic therapy. For non-septic bursitis, aspiration may be combined with corticosteroid injection to reduce recurrence, though injection carries a small risk of skin atrophy, hypopigmentation, and secondary infection if the bursa is inadvertently misclassified.

Ultrasound is often useful for confirming that the swelling is fluid within the superficial olecranon bursa and for guiding aspiration when a clinician needs fluid analysis. X-ray does not diagnose bursitis directly, but it helps look for an olecranon spur, calcification, fracture, or foreign body after trauma. MRI gives the broadest soft tissue view when infection, abscess, osteomyelitis, triceps tendon involvement, or another cause of posterior elbow swelling is a concern.

Surgical excision of the olecranon bursa is reserved for chronically recurrent non-septic bursitis that fails repeated aspiration and conservative measures, or for septic bursitis that does not resolve with antibiotics and percutaneous drainage. Open bursectomy involves complete excision of the bursal sac through a posterior elbow incision, with care taken to avoid violating the triceps tendon. The posterior elbow incision is prone to wound healing complications due to poor skin vascularity and constant motion, and patients should be counseled on a significant wound complication rate compared to operations on other anatomical sites. Endoscopic bursectomy has emerged as an alternative with potentially lower wound complication rates but requires specialized instrumentation.