Background The incidence of childhood bone and joint infections (BJIs) is not well known, but is useful for identifying epidemiological differences and improving practice.

Objective To determine the incidence of BJI in previously well children and describe their clinical, laboratory and radiological characteristics.

Design A multicentre, population-based, prospective study performed from July 2008 through June 2009.

Setting Region of northern France with a population of 872 516 children <16 years old.

Patients All previously well children admitted in the region with septic arthritis, acute osteomyelitis or spondylodiscitis, diagnosed according to consensus criteria and after blinded radiological review.

Main outcome measures The corrected incidence of BJI, determined with a capture-recapture method that used this prospective database and the discharge summary database.

Results 58 cases were identified (median age: 3.6 years, range: 1 month–15.8 years; male to female ratio: 1.6). The completeness of the prospective database was 90%. The corrected incidence of any BJI was 7.1/100 000 children (95% CI 5.3 to 8.9). Thirty patients had septic arthritis (52%, incidence: 3.7/100 000; 95% CI 2.4 to 4.9), 24 osteomyelitis (41%, incidence 3.0/100 000; 95% CI 1.8 to 4.1), 4 spondylodiscitis (7%) and 0 osteoarthritis. Micro-organisms were identified from 15 patients (26%), with Staphylococcus aureus the most frequent organism. Radiological findings were characteristic of infection in 44% of BJI.

Conclusions The corrected incidence of BJI in northern France, according to consensus diagnostic criteria, was 7.1/100 000 children <16 years of age.