Knee osteoarthritis (OA) is being diagnosed at a much younger age than it was about 20 years ago – and it’s expected to place an additional burden on the health care system in the United States. That's according to a study presented at the recent meeting of the American College of Rheumatology in Chicago. The good news, according to a second study presented at the conference, is that that weight loss in combination with exercise can reduce pain and improve function in people with knee OA.

Elena Losina, PhD, co-director of the Orthopaedic and Arthritis Center for Outcomes Research at Brigham and Women’s Hospital in Boston, who presented the first study, suggests that the increased incidence of knee OA in younger adults may be partly related to what the Centers for Disease Control and Prevention has called the national obesity epidemic and to an increasing number of knee injuries.

The study shows that knee OA is diagnosed about 13 years earlier than it was in the 1990s, and the earlier age at diagnosis has led to a dramatic increase in total knee replacement surgeries in people younger than age 65. If the trend continues, it is estimated that more than half of all new diagnoses of knee OA will be in people ages 45 to 64.

“The mean age of onset of physician-diagnosed OA fell from 69 years in the 1990s to 56 years in 2010, according to our study,” says Losina. “Our findings are consistent with the recently observed tripling of total knee replacement use in 45- to 65-year-olds in the U.S. Now about 40 percent of all knee replacements are done in people under age 65.”

But not all of these patients may need surgery. A separate study presented at the conference found that weight loss along with exercise reduces pain and improves symptoms in people with knee OA. The Intensive Diet and Exercise for Arthritis trial evaluated the impact of weight loss and exercise in reducing pain associated with knee OA, and in improving function and mobility in 454 overweight adults with symptomatic knee pain. The diet-alone and the diet-plus-exercise groups were compared to a control group that exercised but did not attempt to lose weight. Exercise consisted of one hour of low to moderate intensity walking and resistance training three days a week.