There have been hundreds of studies on glucosamine and chondroitin, showing their effectiveness for joint health. Recently, the United States National Institutes of Health (NIH) conducted a five–year study (Glucosamine/Chondroitin Arthritis Intervention Trial 2005) and found that glucosamine and chondroitin worked in people with moderate to severe knee pain. In fact, in that group it worked better than other tested alternatives. When the data was expressed as ability to reduce joint pain by 50% or more (the criteria used for pharmaceuitical agents), glucosamine and chondroitin worked for all subjects, but more so in the moderate to severe group.