Background: Osteomyelitis can be difficult to diagnose and there has previously not been a prospective approach to identify all children in a defined geographic area. The aim of this study was to assess the annual incidence of osteomyelitis in children, describe the patient and disease characteristics in those with acute (< 14 days disease duration) and subacute osteomyelitis (≥ 14 days disease duration), and differentiate osteomyelitis patients from those with other acute onset musculoskeletal features.

The annual incidence of childhood arthritis was 71 per 100,000 children. We found several factors that may help in differentiating between subgroups of arthritis.

Streptococcus pyogenes was present in 18% of children with arthritis. The patient characteristics, clinical presentation and early disease course in PSRA was different from that of JIA and transient arthritis.