Clinical decision rule
Kocher Criteria
Kocher Criteria for Septic Arthritis of the Hip
The Kocher criteria estimate the probability that a child with an irritable hip has septic arthritis rather than transient synovitis, using four independent predictors — non-weight-bearing, fever above 38.5 °C, ESR above 40 mm/hour and white cell count above 12,000 — with predicted probability rising from under 0.2% when none are present to over 99% when all four are.
What the Kocher Criteria mean
Kocher Criteria scores run from 0 to 4, where a lower score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Low probability0–1
Transient synovitis is the more likely diagnosis.
- Indeterminate2–2
Neither diagnosis can be excluded on the criteria alone; investigate further.
- High probability3–4
Treat as septic arthritis until proven otherwise.
Published criteria and reliability
The published cut-offs that define this instrument, and the measured agreement between observers using it. Each is reported with the population it was derived in.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | 0 predictors — 0.2% probability | — | Derivation cohort, Boston 1979–1996 | — | Kocher MS 1999 |
| Criterion | 1 predictor — 3.0% probability | — | Derivation cohort, Boston 1979–1996 | — | Kocher MS 1999 |
| Criterion | 2 predictors — 40.0% probability | — | Derivation cohort, Boston 1979–1996 | — | Kocher MS 1999 |
| Criterion | 3 predictors — 93.1% probability | — | Derivation cohort, Boston 1979–1996 | — | Kocher MS 1999 |
| Criterion | 4 predictors — 99.6% probability | — | Derivation cohort, Boston 1979–1996 | — | Kocher MS 1999 |
| Criterion | Predicted probabilities were substantially lower at every predictor count on prospective validation | — | Prospective validation cohort, same institution | — | Kocher MS 2004 |
Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
Four independent predictors are assessed: non-weight-bearing on the affected side, a history or measurement of temperature above 38.5 °C, an erythrocyte sedimentation rate above 40 mm/hour, and a serum white cell count above 12,000 cells/mm³. The number of predictors present maps to a predicted probability of septic arthritis: none 0.2%, one 3.0%, two 40.0%, three 93.1% and four 99.6% in the original derivation cohort. The criteria are a probability gradient, not a diagnostic test, and do not replace joint aspiration where suspicion is high.
Instrument profile
- Developer
- Mininder S. Kocher and colleagues
- Institution
- Boston Children's Hospital, Harvard Medical School
- First published
- 1999
- Items
- 4
- Response format
- Four Yes/No predictors
- Score range
- 0 to 4
- Direction
- Lower score = better
- Completion time
- About 1 minutes
- Age range
- Children, derived in a cohort with a median age of about 5 years
- Regions
- Hip, Paediatric
- Conditions
- Septic arthritis, Transient synovitis, Irritable hip, Paediatric limp
- Validity
- The predictors were independently significant on multiple logistic regression in the derivation cohort, and the rule remains the most widely taught approach to the irritable child’s hip.
- Reliability
- Performance degrades outside the derivation setting. Independent validations have consistently reported lower probabilities at each predictor count, so the rule is best used to stratify urgency rather than to give a patient a number.
When to use the Kocher Criteria
Well suited to
- A child presenting with an acutely painful or irritable hip where septic arthritis and transient synovitis are the competing diagnoses.
- Stratifying urgency and deciding whether to proceed to ultrasound and aspiration.
Limitations and poor fits
- As a reason to withhold aspiration when clinical suspicion is high — a low predictor count does not exclude septic arthritis.
- In neonates, immunocompromised children, or those already on antibiotics, where the inflammatory markers are unreliable.
- For joints other than the hip, and for post-operative or penetrating-injury septic arthritis, which were not in the derivation cohort.
Kocher Criteria compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| CCI | 17 | 0–37 | The Charlson Comorbidity Index is a weighted checklist of 16 comorbid conditions that produces a comorbidity score of 0 to 33, to which up to 4 points are added for age, and which estimates 10-year survival at roughly 98% for a total of 0, 90% for 2, 53% for 4 and 21% for 5. |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
The Kocher criteria are a published clinical prediction rule. The predictors and their probabilities are freely reproducible and no licence is required.
References
- Kocher MS, Zurakowski D, Kasser JR. Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm. Journal of Bone and Joint Surgery (American). 1999.PMID 10608376
- Kocher MS, Mandiga R, Zurakowski D, Barnewolt C, Kasser JR. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. Journal of Bone and Joint Surgery (American). 2004.PMID 15173279
- Caird MS, Flynn JM, Leung YL, Millman JE, D’Italia JG, Dormans JP. Factors distinguishing septic arthritis from transient synovitis of the hip in children: a prospective study. Journal of Bone and Joint Surgery (American). 2006.PMID 16757758
Editorial status
This page has not yet been signed off by a named clinical reviewer. The scoring logic is stated in full above so it can be independently verified, and every threshold is traceable to its source. See our editorial methodology.