A 5-year-old child presents with acute fever, refusal to weight bear, and swelling around the right knee for 3 days. Joint aspiration yields 18,000 WBCs/µL with 92% PMNs, glucose <40 mg/dL, and Gram stain negative. Crystal examination is negative. What is the most appropriate next step?
- A Continue IV antibiotics and repeat aspiration in 48 hours
- B Oral antibiotics and physiotherapy as an outpatient, as WBC <50,000 indicates reactive arthritis
- C Emergency arthrotomy (open joint washout) and IV antibiotics, as the synovial WBC threshold for septic arthritis in this child is met ✓
- D Start steroids for juvenile idiopathic arthritis before aspiration culture results
Explanation
In children, Kocher's criteria for septic arthritis of the hip include: fever >38.5°C, non-weight-bearing, ESR >40 mm/hr, WBC >12,000/µL. Synovial fluid WBC >50,000 cells/µL with >90% PMNs, low glucose, and negative crystals strongly suggests bacterial septic arthritis. However, even 18,000 WBC/µL in a child with this clinical picture (fever, refusal to bear weight, and this biochemical profile) warrants urgent surgical arthrotomy (open joint washout) with debridement and IV antibiotic therapy. Delayed treatment risks permanent joint destruction, chondrolysis, and growth disturbance. Oral antibiotics alone or repeat aspiration are inappropriate when septic arthritis is clinically suspected.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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