Researchers in Japan have identified a gene variant that may be responsible for osteoarthritis, a painful condition in the joints that affects more than 200 million people worldwide.

Osteoarthritis usually develops in old age, when there is a breakdown and loss of cartilage in the joints, leading to swelling and pain, and restricting mobility.

The scientists reported in the journal Nature Genetics that they analyzed DNA from two groups of Japanese patients with hip osteoarthritis and found that the gene variant showed up more frequently in these two patients than in a group of patients without the disease.

The same variant was also significantly more frequent in Japanese and Chinese individuals suffering from osteoarthritis of the knee, the researchers reported.

“Association (between osteoarthritis and the variant gene) was found in Japanese populations and the association was replicated in a Chinese population,” lead researcher Shiro Ikegawa at the SNP Research Center in Tokyo told Reuters.

“Those who have this susceptibility variant are 1.8 times more likely to develop osteoarthritis.”

Explaining the link between the variant gene and osteoarthritis, Ikegawa said the variant probably reduces the amount of growth differentiation factor 5 (GDF5) produced.

GDF5 is a protein that is secreted by cells and is known to be involved in cartilage development, and lower levels of GDF5 may affect the maintenance of cartilage in joints.