Pedemy All toolsAnswer each question. The result gives the probability of septic arthritis, next steps and antibiotic doses. Tap any earlier answer to change it.
This tool helps clinicians tell septic arthritis from transient synovitis in a child with hip pain or a limp. It uses the Kocher criteria with CRP, and gives next steps and weight-based antibiotic doses.
The four Kocher criteria are inability to bear weight, fever over 38.5 °C, ESR over 40 mm/h and WBC over 12,000/mm³. The predicted chance of septic arthritis is under 0.2% with none, 3% with one, 40% with two, 93% with three and 99.6% with all four. A CRP over 2 mg/dL is not part of the original score but is the strongest single predictor. A score of 3 or more, or 2 with a high CRP, means septic arthritis is likely and calls for urgent joint aspiration with orthopedics. A score of 2, or 1 with a high CRP, is intermediate risk and leads to a hip ultrasound and aspiration of any effusion. Lower scores suggest transient synovitis, treated with ibuprofen and a recheck in 24–48 hours.
Antibiotic choices after aspiration follow the PIDS/IDSA 2023 guideline: cefazolin where MRSA is uncommon, clindamycin or vancomycin where it is common, and oral cephalexin to step down, usually for 10–14 days in total. Scoring is based on Kocher 1999 and Caird 2006.
The four criteria are inability to bear weight, fever over 38.5 °C (101.3 °F), ESR over 40 mm/h and WBC over 12,000/mm³. The predicted probability of septic arthritis rises from under 0.2% with none to 3%, 40%, 93% and 99.6% with one to four criteria.
A CRP over 2 mg/dL (20 mg/L) is the strongest single predictor (Caird 2006) and raises concern at any Kocher score. In the tool, a score of 2 plus a high CRP is treated as likely septic arthritis, and 1 plus a high CRP as intermediate risk.
Per PIDS/IDSA 2023, cefazolin is used where MRSA is uncommon and also covers Kingella. Clindamycin or vancomycin is used where MRSA is common. Oral cephalexin is used to step down. Total treatment is usually 10–14 days for uncomplicated septic arthritis.
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