Background and aims Infectious osteoarticular pathology has different clinical, etiological, diagnostic and therapeutic presentation. The aim is to analyse the clinical presentation, diagnosis, therapeutic management and evolution of patients included. Unusual cases identification and their implications.

Methods Retrospective review of admitted patients in the paediatric service of Hospital del Mar and Hospital de Nens de Barcelona with osteomyelitis and septic arthritis diagnosis between 1st January 2000 and 31thAugust 2012.

Results 31 patients with osteomyelitis. Average age of 5.9 years, 35% located in the long bones of the lower extremities. S. aureus isolated in the 41% (etiologic agent not achieved in 48%). On average, the radiography is performed at 5.7 days; the radionuclide bone imaging at 7.1; the nuclear magnetic resonance at 10.8; the ultrasonography at 5.8. Average treatment duration of 46.2 days. Favourable and uncomplicated evolution in 61%.

44 patients with septic arthritis. Average age of 2.6 years, 48% located in the knee. Etiologic agent isolated in the 21%, S. aureus the most prevalent (11%). Arthrocentesis in the 59% and mean treatment duration of 23.1 days. 95% without complications.

Conclusions Increased number of diagnoses of osteomyelitis and septic arthritis in relation to the ER number of visits. S. aureus is the most common etiologic agent, despite the low sensitivity of the collected medical cultivations. All patients have required sequential treatment: initially intravenously and lately orally. Most cases have a good clinical outcome.