Septic arthritis


  • Blood cultures recommended (positive in 60%). If positive, repeat blood cultures to ensure clearance of bacteremia.
  • Synovial fluid for cell count, C&S, and crystal analysis.
    • Typical findings of septic arthritis: purulence, variable viscosity, WBC > 50 x 109/L with > 75% neutrophils. Protein and glucose levels are not diagnostically useful.
    • Gram stain lacks sensitivity (only positive in 1/3); whereas culture is positive in 90%.
    • Tailor antibiotics according to C&S results.
  • CBC and differential, serum creatinine.
  • ESR, CRP - low sensitivity for diagnosis but if initially elevated, may be useful to monitor response.
  • Plain x-ray +/- MRI
    • MRI superior to x-ray and bone scan for early diagnosis of bone/joint infections

- Drainage and/or debridement of the joint space recommended.