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Researchers Investigate Role of Calcium-containing Crystals on Osteoarthritis

Many studies have been done to better understand the presence of calcium-containing crystals in the synovial fluid, the fluid that helps lubricate the joint, in people with osteoarthritis. Researchers do know some of the risk factors for osteoarthritis. They include age, obesity, overuse or misuse of the joint, and calcification of the joint. In this study, the authors wanted to review what research had been done and any advances during the past year.

Basic calcium phosphate (BCP) crystals are often present in the joints of people with osteoarthritis. BCPs are found in as many as 70 percent of cases and researchers feel that this is only the documented number. They believe that the actual percentage is even higher, even perhaps up to 100 percent. Another type of calcium crystals, calcium pyrophosphate dihydrate (CPPD), are also present in some joints with osteoarthritis, but only in 25 percent to 55 percent. Interestingly, one study found that joints with calcium deposits, or chondrocalcinosis did not have as high a risk of losing cartilage as knees without the deposits. Other researchers found that the presence of the CPPD crystals did not seem to have an effect on when the pain started (age), ease or difficulty in performing daily tasks, or if patients had to use a walking aid, such as a cane or walker.

Why the CPPD crystals don't have the same effect as the BCP crystals isn't quite understood. However, there are phosphate ions in the BCP crystals and pyrophosphate ions in the CPPD. Pyrophosphate ions can, potentially, inhibit or block calcification. This is one possible explanation for the difference. Another is that perhaps, unlike BCP crystals, CPPD crystals are not a good way to determine if there is osteoarthritis present. More research, this time from China, has shown that although Chinese men have a rate of osteoarthritis that is similar to white men in the United States, they had a lower rate of calcium deposits than did the Americans. The researchers suggest that this means the calcium deposits and osteoarthritis are not one and the same.

The question of where the crystals come from is likely found in the cartilage, or soft connective tissue in the joints. The crystals in the cartilage are likely released into the synovial fluid as the cartilage breaks down. Other research shows that the calcium crystals help the joint degenerate.

The authors conclude by repeating that the role of the crystals are still not completely understood. It is possible that some of the crystal formation just happens as a part of life, but they may also form because of life activities, aging, or illness. Researchers will have to continue studying the basis of the crystals and their role in osteoarthritis in order to be able to design a medication or treatment to help prevent or reverse the damage.

References: Yubo Sun and Edward N. Hanley Jr. Calcium-containing crystals and osteoarthritis. In Current Opinion in Orthopaedics. September 2007. Vol. 18. No. 5. Pp. 472-478.

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