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Oct. 21, 2009 (Philadelphia) -- Using a more sensitive measure of joint damage than in the past, researchers have found that the popular supplement glucosamine does not appear to slow the progression of knee osteoarthritis.
Previous studies that used X-rays to determine whether glucosamine can prevent joint damage in knee osteoarthritis have produced conflicting results. But it was widely acknowledged that X-rays were less than optimal at spotting bone and cartilage damage.
For the new study, researchers turned to souped-up MRI scanners. MRI itself is far more sensitive than traditional X-rays, and the scanners used in the study are twice as powerful as conventional MRI machines, says C. Kent Kwoh, MD, of the University of Pittsburgh School of Medicine.
"Unfortunately, we did not find any evidence that glucosamine can prevent or slow joint damage in individuals with mild to moderate knee pain," he tells WebMD.
The study involved 201 men and women, average age 52, with mild to moderate knee pain due to osteoarthritis. Participants were randomly assigned to take either 1,500 milligrams of glucosamine hydrochloride or a placebo, once daily.
MRI scans and X-rays were taken of both knees, both at the beginning of the study and six months later.
At the end of the six months, the odds of having worsening cartilage damage were the same in both groups. There was also no significant difference in the chance of having worsening bone damage.
Importantly, the analysis took into account risk factors such as age, sex, body mass index, and pain that could affect the results.
Additionally, when a urine biomarker was used as a basis for comparison, there was no difference in the formation of new cartilage between the two groups.
Kwoh reported the findings at the 73rd Annual Scientific Meeting of the American College of Rheumatology.
Kwoh says this isn't the last word on the effectiveness of glucosamine. While six months is long enough to demonstrate a benefit in terms of pain, "we may have to follow people for longer to see a structural benefit [in the cartilage and bone]," Kwoh says.
Also, interpretation of the results was complicated by the fact that the placebo group had less arthritis progression during the study than the researchers had predicted. "We thought they would do worse," he says.
Additionally, there are two forms of glucosamine supplements: the glucosamine hydrochloride used in the study and glucosamine sulfate. "For now, we are cautioning our patients that if they want to take glucosamine, they might want to consider the sulfate formulation," Kwoh says.
Cleveland Clinic rheumatologist Elaine Husni, MD, who moderated a press conference to discuss the findings, says that not a week goes by in which she is not asked about glucosamine.
"To those who really want to take it, I tell them to try it for three to six months. If it's not working after that, I tell them not to waste their money," she tells WebMD.