Objective. To study the medical and economic impact of osteoarticular infections (OAI) in adults in France. Methods. Hospital stays with an OAI code in their discharge summary were extracted from the 2008 national PMSI databases. A case definition for OAI (with or without implant-associated infection) was developed. Patient characteristics (age, sex, prevalence) and admission characteristics (length of stay, type of care, costs) were analyzed, and factors associated with implant-related infections were identified using logistic regression. Results. OAI affected 28,453 patients (36,091 hospital stays). The mean age was 63.1 years (male-to-female ratio 1.54) and the prevalence was 54.6 per 100,000. Device-related IOA accounted for one-third of cases. When a pathogen was coded (in only 39% of discharge summaries), Staphylococcus spp. accounted for two-thirds of cases. A comorbidity was reported in 47% of cases. Obesity, Staphylococcus spp., male sex, and age over 64 years were strongly associated with infections involving prosthetic devices, whereas diabetes and ulcers were associated with infections of native joints. The case-fatality rate was 4.6%. Health insurance expenditures were estimated at 259 million euros (additional cost for device-related OIs of 1,500 euros per hospital stay). Conclusion. The medico-economic impact of OIs is significant, and the PMSI enables its assessment. This economic burden is associated with significant morbidity, including prolonged hospitalizations and complex care. (R.A.)