Joint needle aspiration compared to tissue samples in septic arthritis of the native knee.

Culture of the causative infectious agent is the only definitive method of diagnosing septic arthritis and can be identified by culture of synovial fluid (SF) or by tissue cultures (TC) obtained at surgery. The aim of this study is to compare the cultures of joint needle aspiration (JNA) with tissue cultures obtained at surgery. 52 patients treated for a suspicion of a septic arthritis of the native knee were retrospectively reviewed. In 84% tissue cultures were equal to joint needle aspiration. Median Gächter classification was 1.0 (range 1-3). 60% of the patients underwent multiple procedures. All patients were successfully treated with an average of 2.0 (range 1-6) arthroscopies. Our results showed that if a patient with a clinical suspicion of septic arthritis is treated, starting antibiotic therapy prior to surgery can be considered, but only after joint needle aspiration to obtain samples for bacteriologic culture. Arthroscopic surgery must be the treatment of choice in Gächter stage 1 to 3, although it might be necessary to perform multiple procedures.