[Epidemiology and physiopathology of osteoarticular infections in children (newborns except)].

Although rare, osteoarticular infections constitute a diagnostic and therapeutic emergency in infants and children. Their incidence has remained stable in the industrialized countries for 20 years. Their evolution has been transformed with the use of antibiotics, mortality has become exceptional and sequelae became rare. Some paediatric specificities of this type of infection are explained by many physiopathological characteristics: bacteriemic inoculation is predominant and corresponds to a particular microbial etiology, the specific vascular and tissue anatomy explains the propensity of articular extension in young infant and the risk of growth sequelae. A generally healthy and richly vascularized ground allows the diffusion of antibiotics and reduces the therapeutic risk of failure and chronicity. Bacterial virulence factors are known principally from a single but prominent agent, Staphylococcus aureus and explain its prevalence (whatever the age) and the potential risk of evolution towards chronicity and the constitution of bone abscesses in adults.