Osteoarthritis commonly affects the knee joint
A new way of scanning joints which may reveal early warning signs of arthritis is being developed by US researchers.
The MRI scan looks for low levels of the chemical glycosaminogycan, which helps cartilage in joints hold the water that makes it tough and elastic.
New York University researchers told the American Chemical Society conference early diagnosis could reduce the need for surgery later in life.
The Arthritis Research Campaign said the scan could help assess treatments.
The weakening and breakdown of cartilage, which cushions the moving parts of joints, is a key factor in the development of osteoarthritis, which is common in the over-40s.
There are an estimated eight million people in the UK who have the problem in some form or another, and in severe cases patients can require constant painkillers or even joint replacement surgery.
Cartilage is tough and elastic because of its high water content, and existing MRI scans look for lower levels of this as a sign that the disease is developing.
The team is trying to spot the disease even earlier by looking for a substance called glycosaminogycan (GAG), which helps the cartilage hold plenty of water.
The scientists found a way to make the hydrogen atoms attached to GAG emit a signal which can be picked up by the scanner.
Dr Alexej Jerschow, one of the researchers, said: "Our methods have the potential for providing early warning signs for cartilage disorders like osteoarthritis, thus potentially avoiding surgery and physical therapy later on."
He said that a patient given early notice of impending arthritis could take steps to protect their joints, perhaps using dietary supplements such as glucosamine and chondroitin, which may be able to slow or halt joint degeneration.
The next stage now is to test the technique in trials.
However, Professor Alan Silman, the medical director of the Arthritis Research Campaign, said that the practical implications of the research were "currently very limited".
"Unfortunately at the moment there is no treatment that could be offered that would change the situation.
"What it may prove to be is a very sensitive test of drug treatment response as new agents are developed."