When should arthrocentesis for synovial fluid analysis be considered in the evaluation of polyarthritis?
When the diagnosis has not been established and joint fluid can be obtained. Both of these requirements need to be met. For example, a patient with obvious OA established by history, physical examination, and radiographs does not require a diagnostic aspiration in an uncomplicated knee effusion. If it can be obtained, synovial fluid analysis can be useful in the diagnosis of bacterial joint infection and crystal-induced arthritis. Even if a specific diagnosis is not forthcoming, synovial fluid analysis reduces the list of diagnostic possibilities by categorizing the process as either inflammatory or noninflammatory.