Dr. Doyt Conn, medical director of the Arthritis Foundation, said the supplements appear to be safe, and they may indeed do some good for some people, but his organization cannot recommend them until there are better scientific data.
"We have to be responsible to the public and give them what reliable information there is to make a judgment," Conn said. "Right now, I don't think that information is out there."
Several U.S. studies are under way, sponsored by companies that make the supplements. The National Institutes of Health is also underwriting one, with results expected in about five years.
Even without the kind of evidence that doctors demand, many hurting people seem willing to try anything that sounds reasonable.
"Pain is a motivator for desperate measures," said Dr. Bobo Tanner, a rheumatologist at Vanderbilt University.
The combination pills, which are widely available in drug and health food stores, typically cost about $40 a month--a lot for someone on Social Security, perhaps, but not an unusual expense for arthritis sufferers. Tanner said his osteoarthritis patients often spent $1,000 a year on unproven remedies. About 10% of them acknowledge taking glucosamine and chondroitin, and at least half have asked about them.
Theodosakis, a sports medicine physician at the University of Arizona who started the craze, estimates that 5 million Americans are taking the supplements. He came across them while trying to relieve his own arthritis, which resulted from sports injuries.
"I needed this stuff, because I was in a wheelchair," he said. "I wasn't helped by anything."
Theodosakis felt a big improvement after two weeks on the supplements. He believes 30% of users will see their arthritis resolve completely, and 80% to 90% will get at least partial relief.
Furthermore, he says, many people find they can reduce their doses over time, and some stop taking the pills entirely without a return of their symptoms.
The most common cause of failure, he says, is brands that contain little or no actual chondroitin and glucosamine. Because the U.S. Food and Drug Administration considers these to be food supplements, not drugs, they escape the kind of scrutiny for purity and effectiveness that medicines receive.
Some arthritis experts are coming around to Theodosakis' view, in part because they have seen remarkable effects in their patients or even in themselves.
Dr. David Hungerford, head of arthritis surgery at Johns Hopkins University, has been taking glucosamine and chondroitin for two years for a bad knee and fingers.
Hungerford is such a believer that he is one of the rare doctors who offers the supplements as first-line osteoarthritis therapy, ahead of anti-inflammatory drugs.
"It's made a dramatic difference for me," he said. "My fingers and joints were swollen and sore. I couldn't use my index finger. Now I have no symptoms at all."
Still, many physicians would probably agree with Dr. Ralph Marcus of Hackensack University Medical Center in New Jersey, who has several hundred patients on glucosamine and chondroitin.
"I can tell you that a very small percentage of patients say they feel better," he said. "My feeling is that somebody's making a lot of money on a product that is probably ineffective."