Synovial fluid lactic acid measurement in the diagnosis and management of septic arthritis.

An improved method of lactic acid estimation by gas liquid chromatography (GLC) is described. Synovial fluid lactic acid estimation was performed on 52 patients (15 with septic arthritis and 37 with non-septic arthropathies) and compared to routine microbiological methods and white cell counts. Lactic acid was found to be a useful and rapid test for differentiating between septic and non-septic arthritis being markedly raised (greater than 12 mmol/l) in all the septic joints. Raised lactic acid concentrations were of particular diagnostic value in patients in whom antibiotic therapy had commenced before joint aspiration. The results of lactic acid estimation on sequential samples were helpful in assessing the response of septic arthritis to treatment.