An office technique for identifying crystal in synovial fluid.

Crystal identification is made with a polarizing, color-compensated light microscope. Most microscopes can be easily and inexpensively adapted for crystal identification. The color compensator allows differentiation between the monosodium urate crystals of gout and the crystals of pseudogout, or calcium pyrophosphate deposition disease. All synovial fluid specimens should be examined. The observation of phagocytosis of crystals establishes that they are the etiologic agent responsible for an ongoing acute attack of arthritis.