A 3-year-old child presents with a 3-day history of fever, pain, and pseudoparalysis of the right hip. Hip X-ray shows lateral displacement of the femoral head. Serum WBC is 18,000/mm³, CRP 120 mg/L. According to Kocher criteria, the predicted probability of septic arthritis is:

• A Low (<0.2%) — no criteria met
• B About 40% — two criteria met
• C About 93% — three criteria met
• D About 99% — all four criteria met ✓

Explanation

The four Kocher criteria for septic arthritis of the hip are: (1) fever, (2) non-weight-bearing, (3) ESR >40 mm/hr (CRP >20 mg/L is the updated equivalent), and (4) WBC >12,000/mm³. When all four are present, the predicted probability of septic arthritis is 99.6%. This child has fever, pseudoparalysis (non-weight-bearing), WBC 18,000, and CRP 120 — all four criteria met. Immediate surgical drainage (arthrotomy or arthroscopic washout) is indicated to prevent avascular necrosis of the femoral head.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.