According to a study losing weight may not help prevent the progression of knee osteoarthritis. More than 2,600 people with the knee ailment were studied who were at high risk for the condition because they were overweight or obese or had other risk factors such as knee pain or previous knee injuries. At the start of the study, patients were given a physical examination and hip bone mineral test and had X-rays taken of both legs and of their knees again after 30 months. D.T. Felson, of Boston University School of Medicine, and colleagues observed that obesity did increase the risk of knee osteoarthritis but that weight had no overall effect on the likelihood of the disease progressing. But it was found that weight had an effect on progression depending on how the knees were aligned. Increased risk of progressive knee osteoarthritis was found in people with high body mass index and neutral alignment and those with valgus (knock-kneed) alignment had a small risk and people with varus (bowlegged) alignment had no increased risk. Regardless of their knee alignment, obesity increased the risk of developing the disease among participants who did not have knee osteoarthritis.