Glucosamine forms part of the extracellular matrix, and we mentioned briefly in class how some people take it to try and treat arthritis. In vitro studies have found that adding glucosamine decreased the levels of cytokines and interleukins while increasing transcription of genes associated with cartilage production. However, there has been much less data that supports the effects of glucosamine in vivo. Two European studies showed that taking glucosamine decreased knee joint-space narrowing over a period of three years; however, the difference compared to a control group was only about 1 mm. Additionally, other clinical studies have shown no significant difference between glucosamine and placebo treatments in treating pain. The bigger problem with using glucosamine as a treatment is that the liver filters out most of the glucosamine before it ever enters the blood stream or comes in contact with any joints.