Not sure how reliable people consider WIKIPEDIA to be, but I read this on there, and wondering what people thought about the study...

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Clinical trials

Due to the popularity of the glucosamine-chondroitin supplement and the lack of reliable information about its usefulness in treating osteoarthritis,[6] the National Institutes of Health funded a study to test the effects of chondroitin and glucosamine on osteoarthritis of the knee. This multicenter, placebo-controlled, double-blind, six month long trial found that glucosamine plus chondroitin had no statistically significant effect on symptoms of osteoarthritis.[7] The control group of patients who took celecoxib (a commonly used osteoarthritis drug) did have a statistically significant improvement in their symptoms. These results indicate that glucosamine and chondroitin do not effectively relieve osteoarthiritic pain. Although the study found no overall effect for the supplements, a secondary analysis of a subgroup of patients suggested that the supplements taken together helped people with more severe pain.