Osteoarthritis, or inflammation of the joints is the most common form of arthritis. Several research studies, including the Chingford Study, and research performed at the University of Southampton, Southampton, England, report that obesity is a major risk factor for developing osteoarthritis in weight bearing joints. This research indicates that both men and women are at risk and that the risk increases with an increase in the Body Mass Index (BMI) of the individual. The increased risk may be caused by the mechanical stress of excess weight or may be due to increased hormone circulation in overweight individuals. The Chingford study found that women with a BMI above 26 were 6 times more likely to get knee osteoarthritis than average weight women. The study also found that being significantly overweight was a cause of hand osteoarthritis, especially at the base of the thumb.