A 4-year-old child presents with fever, refusal to walk, and pseudoparesis of the hip. ESR 80 mm/hr, CRP 45 mg/L, WBC 14,000/mm³, and ultrasound shows joint effusion. Kocher criteria score is 3 out of 4. What is the predicted probability of septic arthritis and what is the appropriate management?

• A Probability ~40% — aspirate under ultrasound and send for culture; treat conservatively if sterile
• B Probability ~93% — IV antibiotics alone for 7 days and reassess
• C Probability ~40% — MRI to differentiate from transient synovitis before any intervention
• D Probability ~93% — immediate surgical drainage under general anaesthesia ✓

Explanation

Kocher criteria are: fever >38.5°C, non-weight-bearing, ESR >40, WBC >12,000 — each scoring 1 point. A score of 3 carries approximately 93% probability of septic arthritis of the hip. Surgical drainage (arthrotomy or arthroscopic washout) is mandatory because pus under pressure in the hip joint rapidly destroys articular cartilage by enzymatic and vascular mechanisms, and can cause avascular necrosis of the femoral head via tamponade effect. IV antibiotics alone are inadequate when pus is present; aspiration alone does not adequately decompress the joint.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.