The first study on twins to explore the question has found that the "obesity" gene has no relevance in osteoarthritis (OA). In a study at St. Thomas? Hospital in London, researchers studied 252 pairs of identical and 574 pairs of fraternal twins, all of them women. Although identical twins have the same genes, the researchers found no real difference in their obesity levels, compared with those of fraternal twins, who share fewer genetic similarities. These results were published in Arthritis & Rheumatism (April 2003). The findings, however, are not suggesting that genetics does not play a role in knee OA, but the genes involved exclude the obesity gene.
"We looked at the osteoarthritis by itself and the individual risks. We looked at twins individually and as pairs.We examined their lifestyle factors and their genetic makeup," rheumatologist and lead author of the study Nisha J. Manek, MD, of the Mayo Clinic, said. "And the genetic link was so minuscule that it was practically nonexistent." She further stated, "It is environmental factors such as diet and lack of exercise that cause knee arthritis. And if you lose weight, you will dramatically decrease your risk of getting knee arthritis and reduce its severity if you already have it."