Crystal arthropathies in osteo-arthritis--clinical aspects and laboratory techniques for crystal identification

Crystal arthropathies are frequent findings in patients with radiographical osteo-arthritis (OA). The associations between cartilage degeneration and crystal deposition of hydroxy-apatite or calcium pyrophosphate dihydrate are not yet understood. However, from the clinical point of view it is important to differentiate synovitis caused by micro-crystals from other symptoms in OA since symptomatic relief is readily obtained with the use of antiphlogistic drugs. Methods to screen synovial fluids for crystals should be introduced in routine clinical practice.