DAVID GREENE, HOST:
Twenty-seven million people in this country have joint pain because of osteoarthritis. And sales of a supplement that's supposed to help them are booming. It's a supplement called glucosamine chondroitin.
NPR's Patti Neighmond reports on how well it works.
PATTI NEIGHMOND, BYLINE: Here's the rationale for why the supplement might help. Glucosamine and chondroitin are both natural substances found in and around the cartilage of the joints. Rheumatologist Allen Sawitzke at the University of Utah says they're found in the cells of cartilage.
ALLEN SAWITZKE: Cartilage is - got cells in it like the rest of the body but it also has what we call matrix, which is just proteins and kind of like Jell-O, I guess we'll call it.
NEIGHMOND: And that Jell-O-like substance is what protects joints when knees or hips are jolted. It also helps with flexibility.
And because osteoarthritis is a wear and tear disease - where cartilage actually degenerates - the idea is that taking extra glucosamine and chondroitin might help maintain and even repair the damage.
Findings from a large study Sawitzke worked on suggest that for certain patients with osteoarthritis of the knee, there may be some benefit.
SAWITZKE: In people with moderate to severe pain there seemed to be some relief.
NEIGHMOND: Those patients reported 25 percent greater pain relief than those taking other treatments or a placebo. But it was a small number of patients, and in fact, the vast majority of people in the study who took the supplements did no better than those who took the placebo.
David Felson is a rheumatologist at Boston University School of Medicine.
DAVID FELSON: Meaning that it didn't relieve pain any better than placebo; meaning that it didn't affect the structure of the joint - they got x-rays to evaluate structure of the joint; that it didn't cause any delay in the structural progression of the disease compared to placebo - that it basically didn't have any affect.
NEIGHMOND: Even so, sales of the supplement are in the hundreds of millions of dollars a year. Felson says that's largely due to hype.
FELSON: There's a lot of advertising out there that suggests that glucosamine is effective and chondroitin is effective, even though the best evidence suggests they don't work.
NEIGHMOND: So, the question for most people is simple: Are they wasting their money buying these supplements?
PATIENCE WHITE: Anything that can help people with their pain is wonderful.
NEIGHMOND: Dr. Patience White is a rheumatologist and spokesperson for The Arthritis Foundation.
White says the placebo effect is powerful. And in the study 60. percent of patients taking a placebo reported significantly less pain. And if people feel less pain - no matter what the reason, she says - that's a good thing.
WHITE: My goal as a practicing physician is to decease pain so they'll actually do the things that really make a difference in terms of changing the natural history of osteoarthritis, which is weight reduction and physical activity - both of which people won't do when they hurt.
NEIGHMOND: And White says there's been lots of research proving that the most effective treatments for osteoarthritis, particularly of the knee, is exercise and weight loss.
WHITE: It's quite striking that if you lose only five pound you're talking about the equivalent of 20 pounds across those knees so you can imagine it would make quite a difference.
NEIGHMOND: And, when it comes to exercise, rheumatologist David Felson says it really doesn't matter what kind you do.
FELSON: There've been a variety of different exercise studies which have tried anything from water aerobics, to walking, to muscle strengthening and they all seem to work.
NEIGHMOND: Probably by boosting muscle strength - around the failing joint. So exercise is definitely the way to go, but if you're taking glucosamine chondroitin supplements anyway, and you think they help - then Felson says here's no harm in doing it. The supplements have been shown to be safe.
Patti Neighmond, NPR News.