Crystals, inflammation, and osteoarthritis.

Calcium pyrophosphate and apatite crystals are common in osteoarthritic knee effusions. One or the other crystal was found in 60 percent or more of cases. These crystals offer the potential for mechanical effects in cartilage but are also often phagocytized by synovial cells. A low-grade inflammation with release of proteases and other mediators of inflammation may be an important factor in the pain and joint damage of osteoarthritis. Crystal-associated changes may merit specific attention in any future approach to therapy.