Kocher criteria (septic arthritis of the hip)
Septic arthritis versus transient synovitis in children with an acutely irritable hip
Sources last checked: 2026-11-03
Kocher criteria (septic arthritis of the hip)
Septic arthritis versus transient synovitis in children with an acutely irritable hip
Predicted probability of septic arthritis < 0.2 % in the 1999 derivation.
Derived retrospectively at one tertiary children's hospital; in the prospective validation the area under the ROC curve fell from 0.96 to 0.86, so the probabilities are overestimates outside the derivation cohort. The criteria support, but do not replace, ultrasound and joint aspiration when septic arthritis is suspected.
Interpretation
| 0 predictors | Predicted probability of septic arthritis < 0.2 % in the 1999 derivation. |
|---|---|
| 1 predictor | Predicted probability of septic arthritis 3.0 % in the 1999 derivation. |
| 2 predictors | Predicted probability of septic arthritis 40.0 % in the 1999 derivation. |
| 3 predictors | Predicted probability of septic arthritis 93.1 % in the 1999 derivation. |
| 4 predictors | Predicted probability of septic arthritis 99.6 % in the 1999 derivation. |
What is the Kocher criteria (septic arthritis of the hip)?
The Kocher criteria estimate the probability of septic arthritis rather than transient synovitis in a child with an acutely irritable hip. Kocher, Zurakowski and Kasser identified four independent predictors — history of fever, non-weight-bearing, ESR ≥ 40 mm/h and white cell count > 12 × 10⁹/L — in a retrospective cohort at a Boston children's hospital (JBJS Am 1999). The same four predictors were confirmed in a prospective validation in 2004, with lower discrimination.
When to use it
- Children with an acutely painful hip, limp or refusal to bear weight, when septic arthritis is in the differential.
- Structuring the decision for hip ultrasound, aspiration or orthopaedic referral.
- Explaining risk to parents and colleagues with a probability rather than a gestalt.
When not to use it
- Joints other than the hip — the rule was derived for the hip only.
- Neonates, immunocompromised children, or children with known joint disease.
- As a reason to delay aspiration in a clearly septic child.
How it is calculated
| Criterion | Points |
|---|---|
| History of fever | +1 |
| Non-weight-bearing | +1 |
| ESR ≥ 40 mm/h | +1 |
| Serum white blood cell count > 12 × 10⁹/L | +1 |
Clinical pearls and limitations
- Derived retrospectively at one tertiary children's hospital; in the prospective validation the area under the ROC curve fell from 0.96 to 0.86, so the probabilities are overestimates outside the derivation cohort. The criteria support, but do not replace, ultrasound and joint aspiration when septic arthritis is suspected.
- The probabilities rise steeply: 3 % with one predictor, 40 % with two and 93 % with three in the derivation.
- In the prospective validation the AUC fell from 0.96 to 0.86, so the derivation percentages overestimate risk.
- CRP is not part of the original four criteria, although later work has studied it as an additional predictor.
- Recent antibiotic use can blunt fever and laboratory markers.
Frequently asked questions
What are the Kocher criteria?
History of fever, non-weight-bearing, ESR ≥ 40 mm/h and serum white cell count > 12 × 10⁹/L (12,000/mm³). The number present maps to a predicted probability of septic arthritis.
What is the probability of septic arthritis with 3 Kocher criteria?
93.1 % in the 1999 derivation; with all four it was 99.6 %, with two 40.0 %. Validation cohorts found lower values.
How do you tell septic arthritis from transient synovitis of the hip?
Clinical features and inflammatory markers such as the Kocher criteria guide the probability; joint aspiration with cell count and culture is the definitive test.
Evidence and guidelines
- Primary source: Kocher MS, Zurakowski D, Kasser JR. Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm. J Bone Joint Surg Am 1999;81(12):1662-1670.
- Kocher MS, Mandiga R, Zurakowski D et al. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am 2004;86(8):1629-1635.
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