After 18 months, among the 399 adults who completed the study, the group who dieted and exercised lost 11.4 percent of their body weight, the group that just dieted lost 9.5 percent of body weight, and the exercise-only group lost 2.2 percent of their body weight. The diet-plus-exercise group also had the best outcomes for reduced pain – by about 50 percent – and for improved function and mobility.

“Clinicians can tell their patients that they will see marked improvement in pain and function in six months or less with intensive diet and exercise, but significant differences favoring intensive diet and exercise may take as long as 18 months to appear,” says lead author Stephen P. Messier, PhD, professor and director of the J.B. Snow Biomechanics Laboratory and Wake Forest University Runners’ Clinic at Wake Forest University in Winston-Salem, N.C.

A third study presented at the conference may relieve worries that exercise and sports will lead to knee OA.

“Most sports probably don’t increase the risk of knee OA, especially if participation is recreational. People who want to reduce their risk of knee OA should participate in non-contact and low-impact sports, such as doubles tennis, swimming and cycling,” says lead author Jeffrey B. Driban, PhD, research associate at Tufts Medical Center in Boston.

Driban and colleagues looked at 16 studies with a total of 3,192 participants and found that knee OA occurred in 8.4 percent of former sports participants compared with 9.1 percent of people who did not participate in sports, suggesting that sports activity does not generally increase the risk of knee OA. However, the risk was higher in soccer players as well as elite long-distance runners, weight lifters and wrestlers – sports that involve weight bearing on the knee.

Scott J. Zashin, MD, clinical professor of medicine at the University of Texas Southwestern Medical School in Dallas, cites several possible reasons for the increase in knee OA among younger people: increased awareness by physicians as well as by patients seeking help for their symptoms; obesity; and more children playing soccer at younger ages and playing it year-round.

“I tell my patients that every 1 pound of body weight is equivalent to 4 pounds of weight on your knee,” Dr. Zashin says. “One of the best treatments that doesn’t involve medications is maintaining one’s ideal body weight.”