I don't think there's enough evidence yet and my doctor agrees. There are also risks. Here are some notes I've saved with links to the entire articles.
MSM (methylsulfonylmethane) is hyped as a treatment for arthritis pain as well as for a long list of other ailments - everything from constipation to snoring - but there have been no human studies to prove or disprove any of the claims.
http://www.drweil.com/drw/u/id/QAA43373
Do You Need Glucosamine?
It is possible that incorporating daily glucosamine supplements may rectify and replace falling levels in the body and reduce osteoarthritis symptoms, although studies have yielded contradictory results.
Some studies have shown glucosamine and chondroitin sulfate taken together may increase effectiveness in relieving arthritis pain, but more research is needed to establish a clear therapeutic effect. Most studies have shown that glucosamine needs to be taken for 2 - 4 months before its full benefits are realized, although many experience some improvement sooner. Glucosamine can be used safely in conjunction with non-steroidal anti-inflammatory drugs (NSAIDs).
http://www.drweil.com/drw/u/ART03241/Glucosamine.html\
MSM is a chemical found in plants, animals, and humans. It can also be made in a laboratory. People use it as a medicine.
You may have heard about MSM because of the book The Miracle of MSM: The Natural Solution for Pain. There isn't much published scientific research to support its use.
Contrary to some MSM promotional literature, there is no Recommended Dietary Allowance (RDA) for MSM or sulfur, which it contains. Sulfur deficienty has not been described in the medical literature.
How does it work?
MSM might supply sulfur to make other chemicals in the body.
http://www.webmd.com/vitamins-suppl...ylsulfonylmethane.aspx?activeingredientid=522
Why do people take glucosamine sulfate?
The supplement seems to reduce pain as much as ibuprofen. But it doesn't work as fast. It can take four to eight weeks for glucosamine sulfate to ease pain.
Glucosamine may affect blood sugar and insulin levels. However, studies are mixed. Talk to your doctor before taking this supplement if you have diabetes or insulin resistance.\further increase LDL "bad" cholesterol levels if you eat a lot of fatty foods. More research is needed.
Talk to your doctor before using this supplement if you are allergic to shellfish.
http://www.webmd.com/vitamins-and-supplements/glucosamine-sulfate-uses-and-risks?page=2
Why do people take chondroitin?
As an osteoarthritis treatment, chondroitin is often used along with another supplement, glucosamine.
The evidence that chondroitin helps with osteoarthritis is mixed. A number of studies seemed to show that it is effective. Researchers found that chondroitin appeared to reduce pain, increase joint mobility, and decrease the need for painkillers.
Several found that chondroitin supplements had only a small benefit, if any.
People who have shellfish allergies, asthma, or prostate cancer should not take chondroitin supplements without talking to a doctor first. Since chondroitin might work as a blood thinner, there is a theoretical risk of bleeding, especially in people with bleeding disorders.
http://www.webmd.com/diet/supplement-guide-chondroitin