Differentiate Children Septic and Inflammatory Arthritis by Comparative Analysis

Inclusion Criteria: Group A and group B: * Subject of more than 6 months and under age 15 years, * Presenting acute arthritis taken care in the University Hospitals of Montpellier, Nimes, Toulouse or Lyon, and requiring an articular puncture, * Child benefiting from a social security system, * Collection of the consent of the legal parents/representatives, Group C: * Subject of more than 6 months and under age 15 include, * Taken care in the University Hospital of Montpellier, and requiring a venous draining, * Child benefiting from a social security system, * Collection of the consent of the legal parents/representatives Exclusion Criteria: Group A and group B: * Contraindication in an articular draining: platelet 50 000/mm3, pathologic hemostasis * Treatment by biological therapy, corticoids or other immunosuppressant treatment in the month preceding the articular draining, * antibiotic begun more than 24 hours before the inclusion. Group C: * Patient achieves of an inflammatory chronic pathology * Patient having presented an infectious episode in the previous 8 days * Patients under immunosuppressor or anti-infective