A key gene which appears to increase the risk of developing osteoarthritis has been found by scientists.
Osteoarthritis affects 5% of the adult population
Osteoarthritis, the most common form of arthritis, affecting over 5% of adults, causes the progressive loss of protective cartilage in the joints.
Japan's Institute of Physical and Chemical Research found a mutant form of a gene called asporin was more common in osteoarthritis patients.
The research is published in the journal Nature Genetics.
The scientists, who focused on Japanese patients with knee or hip osteoarthritis, also found that the more severe the disease, the more likely the mutant form of asporin was to be present.
To keep cartilage tissue healthy and functioning properly, the body must strike a delicate balance between breaking down cartilage that has come to the end of its useful life, and replacing it with fresh tissue.
If the degradation of cartilage is outstripped by production of new tissue, then osteoarthritis can result as the unprotected ends of the bones rub together, causing inflammation.
It is thought that asporin plays a role in regulating the production of new cartilage by impacting on growth factors which trigger its development.
It may be that the mutant form of the gene reduces the impact of growth factors too much, slowing down cartilage production so that degraded tissue is not effectively replaced.
Dr Madeleine Devey, medical advisor to the Arthritis Research Campaign, welcomed the study.
"It's a very important paper which identifies a susceptibility gene for OA and also provides some clues as to its functional importance in cartilage degradation.
"It adds another piece to the jigsaw of understanding OA and also may provide a promising target for therapy."
Professor Anthony Woolf, an expert in rheumatology at Royal Cornwall Hospital, Truro, told the BBC News website: "Osteoarthritis is a major cause of disability worldwide, from which almost 10% of men and 20% of women over 60 years suffer.
"This research gives us a greater understanding of the causes of osteoarthritis which may one day lead to better treatment and that is now the challenge."