The nutraceuticals glucosamine and chondroitin seem to have overall efficacy in treating symptoms of osteoarthritis but estimates of benefit are "inflated", according to Dr Timothy McAlindon and colleagues (Boston university school of medicine, Boston, Massachusetts, US).
They report in the Journal of the American Medical Association (2000;283:1469) a meta-analysis of 15 trials, involving the use of either of the two products to treat osteoarthritis of the hip or knee. They found moderate treatment effects for glucosamine and large effects for chondroitin but, they say, the actual efficacy is likely to be "substantially more modest" because of publication bias and flawed methodology.
The modes of action of glucosamine and chondroitin are not known but they appear to increase proteoglycan synthesis in articular cartilage, say the authors.
An editorial commenting on the results of the meta-analysis (ibid, p1483) says that the side effects of glucosamine and chondroitin are not summarised in the paper, which makes it difficult to know whether any benefit is worth the potential risks. In addition, long term efficacy and the consistency of different products have not been established.