A 3-year-old boy refuses to walk after a minor fall yesterday. He is afebrile, temperature 37.1 C, holding the right hip in flexion with external rotation. WBC is 9,500/mm3, ESR 22 mm/hr, CRP 8 mg/L, and hip ultrasound shows a small effusion. According to the Kocher criteria, what is the next best step?

• A Reassure and discharge with analgesics
• B Ultrasound-guided joint aspiration for Gram stain and culture ✓
• C Start oral antibiotics and follow up in clinic
• D MRI of the pelvis before any intervention

Explanation

Kocher criteria are fever, nonweightbearing, ESR above 40 mm/hr, and WBC above 12,000/mm3. This boy meets one criterion, giving a low probability of septic arthritis, but he does meet the criterion of refusal to bear weight and has an effusion; with any uncertainty in a young child, aspiration is the decisive step because untreated septic arthritis destroys the femoral head within days. Simple reassurance risks missing infection, and MRI delays source control.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.