What is the treatment for septic prepatellar bursitis?

Treatment of Septic Prepatellar Bursitis

The treatment of septic prepatellar bursitis requires immediate joint drainage combined with appropriate antibiotic therapy, with surgical drainage indicated in all cases to effectively eliminate the infection and prevent complications. 1

Diagnosis

• Suspect septic prepatellar bursitis in patients with:

  • Acute swelling over the anterior knee
  • Erythema and warmth
  • Pain with movement
  • Fever (more common in prepatellar than olecranon bursitis - 71% vs 48%) 2
  • Leukocytosis (76% of prepatellar cases) 2
  • Cellulitis (59% of prepatellar cases) 2

• Diagnostic workup:

  • Aspiration of bursal fluid for:
    • Cell count (typically >1000 cells/mm³) 3
    • Gram stain
    • Culture
  • Blood cultures (positive in 25% of prepatellar septic bursitis) 2
  • Inflammatory markers (ESR, CRP)

Microbiology

• Staphylococcus aureus is the predominant pathogen (87.5% of cases) 2
• Less common organisms:
  • Staphylococcus epidermidis
  • Streptococcal species (including S. agalactiae and S. pneumoniae)
  • Beta-hemolytic Streptococcus 4

Treatment Algorithm

1. Drainage

• Bursal drainage is essential and should be performed promptly 1
• Options include:
  • Needle aspiration (may need to be repeated)
  • Percutaneous tube placement for suction-drainage 4
  • Surgical incision and drainage for severe cases or when conservative measures fail

2. Antimicrobial Therapy

• Start empiric antibiotics immediately after obtaining cultures 1

• Initial empiric coverage should include:

  • MRSA coverage with IV vancomycin (B-II) or daptomycin 6 mg/kg/day IV (B-II) 1
  • Consider broader coverage if polymicrobial infection is suspected

• Once culture results are available:

  • De-escalate to targeted therapy based on susceptibilities 5
  • For methicillin-sensitive S. aureus: nafcillin, oxacillin, or cefazolin
  • For MRSA: continue vancomycin, daptomycin, or transition to oral options like trimethoprim-sulfamethoxazole, doxycycline, or linezolid

3. Duration of Therapy

• Total antibiotic course of 2-3 weeks is typically required 1
• IV therapy duration averages 11 days (range: 5-21 days) 2
• Transition to oral antibiotics when:
  • Clinical improvement is evident
  • Inflammatory markers are decreasing
  • Patient is afebrile

4. Adjunctive Measures

• Rest and elevation of the affected limb
• Immobilization as needed for comfort
• Regular monitoring of inflammatory markers
• Repeat aspiration if reaccumulation occurs

Special Considerations

• Local antibiotic irrigation may be beneficial in severe cases

  • A solution of antibiotics (such as 1% kanamycin and 0.1% polymyxin) has been used successfully 4
  • This approach showed no complications or recurrences in a small study 4

• Surgical bursectomy should be reserved for:

  • Recalcitrant cases not responding to conservative treatment
  • Note: Open bursectomy carries risk of skin necrosis and other surgical site complications 6

• Predisposing factors that should be addressed:

  • Occupational or recreational trauma (55% of cases) 2
  • Steroid therapy (15% of cases) 2
  • Alcoholism (8% of cases) 2
  • Cutaneous lesions that may serve as entry points

Prognosis

With prompt diagnosis and appropriate treatment:

• 95% of cases can be successfully treated without open surgical drainage 2
• No functional impairment, serious complications, or recurrences were observed in a study of 40 patients 2
• The duration of antibiotic treatment necessary correlates with how long the infection has been present 7

Pitfalls to Avoid

1. Misdiagnosis as nonseptic bursitis - Always perform bursal fluid analysis to distinguish septic from nonseptic causes 3
2. Inadequate drainage - Relying solely on antibiotics without adequate drainage may lead to treatment failure
3. Insufficient antibiotic duration - Premature discontinuation of antibiotics before complete resolution
4. Failure to recognize bacteremia - Prepatellar septic bursitis has higher rates of positive blood cultures than olecranon bursitis 2
5. Delayed treatment - Longer duration of infection requires longer antibiotic treatment 7