What is the treatment plan for an otherwise healthy adult with septic bursitis of the prepatellar bursa?

Treatment of Septic Prepatellar Bursitis

For an otherwise healthy adult with septic prepatellar bursitis, initiate treatment with bursal aspiration plus antibiotics targeting Staphylococcus aureus, reserving surgical drainage for severe cases or those unresponsive to initial management. 1, 2

Initial Diagnostic Confirmation

Before initiating treatment, confirm the diagnosis through bursal aspiration with fluid analysis:

• Aspirate findings suggestive of septic bursitis: purulent fluid, white cell count >3,000 cells/μL, polymorphonuclear cells >50%, fluid-to-serum glucose ratio <50%, positive Gram stain, or positive culture 3
• Clinical findings supporting infection: fever >37.8°C, prebursal temperature difference >2.2°C, or overlying skin lesions 3
• Send aspirate for: Gram stain, bacterial culture with sensitivities, crystal analysis, glucose measurement, and cell count with differential 2, 3

Critical caveat: The surrounding erythema should be termed "septic bursitis with surrounding inflammation" rather than "cellulitis," as this distinction guides proper treatment requiring drainage plus antibiotics rather than antibiotics alone 1

Antibiotic Therapy

Start empiric antibiotics effective against Staphylococcus aureus, which accounts for approximately 80% of septic bursitis cases 2, 4:

• For outpatient management (non-acutely ill patients): oral antibiotics targeting S. aureus 2
• For hospitalized patients (acutely ill): intravenous antibiotics 2
• Adjust antibiotics based on culture results and sensitivities; consider coverage for atypical organisms like Pseudomonas aeruginosa in immunocompromised patients 4
• Duration: Average antibiotic course is approximately 19-24 days based on clinical response 5

Drainage Strategy

Perform initial bursal aspiration as both a diagnostic and therapeutic intervention 2, 3:

• Aspiration alone may be sufficient for mild cases when combined with appropriate antibiotics 3
• Reassess effectiveness regularly within 48-72 hours; persistence of fever or worsening symptoms indicates treatment failure 6

Escalate to surgical drainage when: 1, 2

• Severe septic bursitis at presentation
• Failure to respond to initial aspiration plus antibiotics within 7 days
• Recurrent septic bursitis

Surgical Options

When surgical intervention is required:

• Percutaneous suction-irrigation system: Place tube for continuous suction-drainage with local antibiotic irrigation (1% kanamycin and 0.1% polymyxin solution); this controlled infection in all 12 cases in one series with no recurrences 5
• Endoscopic bursectomy: Minimally invasive option with average hospital stay of 6 days and return to work in 18 days, with no wound complications or recurrences reported 7
• Open bursectomy: Reserved for refractory or chronic/recurrent cases, though carries higher risk of wound complications including skin necrosis and prolonged recovery 7, 3

Important pitfall: Immediate bursectomy is not supported by evidence and should be avoided; conservative management with aspiration and antibiotics should be attempted first 3

Adjunctive Measures

Implement general supportive care alongside definitive treatment:

• PRICE protocol: Protection, Rest, Ice, Compression, Elevation 3
• NSAIDs for pain and inflammation control 3
• Avoid corticosteroid injections in confirmed or suspected septic bursitis, as this is contraindicated 8, 2

Monitoring and Follow-up

• Reassess clinical response within 48-72 hours of initiating treatment 6
• Common causes of treatment failure: inadequate antimicrobial coverage, insufficient drainage, development of antibiotic resistance, or misdiagnosis 6
• If worsening or no improvement by 7 days: change antibiotics if already started, or escalate to surgical drainage 6, 1