Both glucosamine and chondroitin are natural substances found in and around the cells of animal cartilage. They are sold as dietary supplements and regulated as food, not drugs. The two compounds are often combined in one dose to "maximize" their effect... but do they truly work?
The answer isn't so simple. Early, small studies indicated patients saw some improvements with joint pain and mobility. In fact, many swear by their effectiveness. Yet recent... more exhaustive research funded by the National Institutes on Health found that glucosamine and chondroitin were no more helpful than the placebo given to patients with minor pain caused by osteoarthritis.
Those who suffered with severe pain fared only slightly better than those who got the placebo.
The good news is that taking glucosamine and condroitin... alone or together is safe and has few side effects... unless you consider spending your money on questionable supplements a side effect. And buyers beware this research found that brands varied widely in quality and quantity.
More studies may help find a consensus... but for now my recommendation is that if you are currently taking the compounds and you think they work for you there's probably some help. But if you aren't taking them, the latest evidence unfortunately says hype.