The natural supplements glucosamine and chondroitin appear to beat the leading prescription drug for very painful forms of arthritis, according to a study sponsored by the National Institutes of Health.

Looking at nearly 1,200 patients with osteoarthritis of the knee, about 79 percent of those who took both supplements experienced relief for moderate to severe pain, compared to 69 percent of those who took Celebrex. The natural duo was also better than taking either supplement alone.

Dr. Daniel Clegg, a rheumatologist at the University of Utah who led the study, expressed caution over some of the findings. When tested in mild osteoarthritis, glucosamine and chondroitin did not even beat a placebo, possibly because the slight changes in pain are harder to detect.

Overall, Celebrex out performed the two supplements when all the patients were combined in the final tally. But in what researchers called an "exploratory analysi", a much smaller number of patients with severe pain responded best to glucosamine and chondroitin.

Celebrex belongs to the troubled class of drugs known as COX-2 inhibitors, which have come under scrutiny after Vioxx and Bextra were withdrawn for potential heart related side-effects.

Although Celebrex has not been associated with the same high number of heart attacks, doctors have expressed increasing concerns about the drug, causing sales for the once top-selling arthritis treatment to decline.