Kocher Criteria for Septic Arthritis

Introduction
The Kocher Criteria is applicable to all children with an acutely irritable hip when the differential diagnosis includes septic arthritis and transient synovitis.

• Septic arthritis and transient synovitis can be difficult to distinguish due to their similar, non-traumatic presentations.

• The Kocher Criteria can help to identify children at greater risk who may need urgent orthopedic consultation versus outpatient observation.

The Kocher Criteria uses 4 criteria to rule in or rule out septic arthritis in the pediatric population. According to the validation study (Kocher et al, 2004), children falling on either extreme of the criteria can be readily ruled in or out. However, the criteria in the intermediate range (1-2 criteria) did not perform as well.

Rules & Recommendations

1. Criterion: 3% probability for septic arthritis

   • In well-appearing children with no predictors present and a low clinical suspicion for septic arthritis, consider observation and/or discharge with close follow-up.

   • The Kocher Criteria performs well when pediatric patients fall on either extreme of the criteria, and can be ruled in or out for septic arthritis.

2. Criterion: 40% probability for septic arthritis

   • In children with a clinical concern for septic arthritis and at least one predictor present, may need further work-up and intervention, such as radiology or orthopedics consultation for hip aspiration.

   • In the validation study, criteria did not perform as well in the intermediate range (1-2 predictors) than those on either extreme of the criteria.

3. Criterion: 93% probability for septic arthritis

   • Urgent orthopedic consultation: Greater likelihood child may require surgical drainage. Consider aspiration in the operating room instead of the radiology suite. 

4. Criterion: 99.6% probability for septic arthritis

   • Urgent orthopedic consultation: Greater likelihood child may require surgical drainage. Consider aspiration in the operating room instead of the radiology suite. 

   • The Kocher Criteria performs well when pediatric patients fall on either extreme of the criteria, and can be ruled in or out for septic arthritis.

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 Dec;81(12):1662-70. doi: 10.2106/00004623-199912000-00002. PMID: 10608376.