Septic Bursitis (Olecranon / Prepatellar)

The olecranon and prepatellar bursae are superficial, lying between skin and a bony prominence where they reduce friction; this exposes them to repetitive pressure (kneeling/leaning) and abrasions, which can inoculate organisms directly. Septic bursitis therefore commonly follows minor trauma to the elbow or knee, especially in manual/kneeling workers, and is more frequent with diabetes, immunosuppression, gout and rheumatoid disease. Patients present with a warm, red, tender, fluctuant swelling over the bursa; features favouring a septic rather than non-septic cause are greater erythema and warmth, peri-bursal tenderness, surrounding cellulitis and systemic features (fever) - though clinical differentiation is unreliable, hence the need for aspiration.

• Aspiration: the key test - send bursal fluid for Gram stain, culture, cell count and crystals (which also diagnoses gout/pseudogout). Aspirate through healthy skin away from the inflamed area to avoid a chronic sinus. Add WCC/CRP; image only if a foreign body or deeper collection is suspected.
• Confirm it is bursitis, not septic arthritis: check that passive joint movement is preserved and relatively painless.
• Antibiotics (mainstay): anti-staphylococcal (e.g. flucloxacillin), oral for mild cases and IV if there is fever or extensive cellulitis, refined by culture; treat for at least ~14 days (shorter courses fail more often).
• Surgery: reserve incision and drainage or bursectomy for an abscess, a foreign body, or failed medical therapy; medical and surgical management have equivalent success, so antibiotics are first-line for uncomplicated cases.
• Adjuncts: rest, compression, elevation, avoid further pressure/trauma.