Study: Diet and Exercise is Effective Knee Arthritis Treatment

A clinical trial has shown that diet and exercise effectively can ease knee osteoarthritis in overweight and obese patients better than either therapy on its own.

The combination of both therapies significantly improved joint inflammation, pain, function, and quality of life over 18 months compared with exercise alone, Stephen P. Messier, Ph.D., and his colleagues at Wake Forest University in Winston-Salem, N.C., found.

Comparing single strategies, diet was better than exercise for reducing knee joint loading and cutting inflammation, the group reported in the Journal of the American Medical Association.

The mean weight loss was 11.4 percent of body weight in the combined diet and exercise group compared with 9.5 percent in the diet-alone group and 2 percent in the exercise-alone group (P<0.001 for both diet groups versus exercise alone). All three strategies had a target of 10 percent or greater loss in body weight with a high level of support as indicated by the trial's name, Intensive Diet and Exercise for Arthritis (IDEA).

“This gives us some real guidelines for what kind of change needs to happen to be meaningful,” Amanda E. Nelson, M.D., M.S.C.R., a rhematologist at the University of North Carolina at Chapel Hill, told MedPage Today. “So we can tell patients if they’re going to lose 10 percent of their body weight, they can expect these kind of benefits and in order to do that, the kind of diet restrictions and the kind of exercise regimens that are required.”

The ways in which patients achieve weight loss remains unclear, however. Researchers are not sure whether the types of exercise other than the aerobics and strength training used in the trial or different diets can achieve the same benefits for arthritic knees, Nelson pointed out.

The trial included 454 community-living participants ages 55 and older with mild or moderate knee osteoarthritis and a body mass index in the 27 to 41 kg/m2 range. The analysis included 399 who remained with the trial to month 18 (88 percent).

All patients had a sedentary lifestyle and were randomized to one of three open-label interventions:

• Intensive weight loss with meal replacement shakes, substantial caloric restriction (800 to 1,000 kcal daily below intake), weekly or biweekly nutrition education and behavioral group sessions, and periodic individual support sessions;
• An aerobic and strength training exercise intervention for one hour, three days a week, initially at a center then with the option for a home-based regimen; and
• Both diet and exercise interventions.

Any patient who had trouble reaching the 10 percent body weight loss target received extra individual and group counseling, social support, and incentives. The primary endpoints were objective mechanistic measures, rather than symptom driven.

Peak knee compressive force as a measure of knee joint loading at 18 months showed a 5 percent decline in the exercise group, a 10 percent drop in the diet group, and a 9 percent decrease in the combination group (148, 265, and 230 Newtons per step, respectively), a difference which was significant only for the exercise-alone versus diet-alone comparison (P=0.007).

Plasma interleukin-6 as a measure of inflammation implicated in osteoarthritis pathogenesis was 0.43 pg/mL lower in the diet group versus exercise alone (P=0.006) and 0.39 pg/mL lower in the diet and exercise group (P=0.007).

For secondary endpoints, pain scores were lowest with the combination intervention, significantly so compared with exercise alone (3.6 versus 4.7 on the 20-point scale, P=0.004) and diet alone (3.6 versus 4.8, P=0.001).

Functional scores also were best with the combination, with a significant difference versus exercise alone (14.1 versus 18.4 on the 68-point scale, P<0.001) and versus diet alone (14.1 versus 17.4, P=0.003).

Health-related quality of life was best with diet and exercise intervention combined, again with a significant difference versus exercise alone (44.7 versus 41.9 on the 100-point SF-36 scale, P=0.005).

The benefits for compressive force, inflammation, pain, and function correlated with the amount of weight lost.

Researchers said the study was designed to detect a greater impact on knee joint loading and inflammation than the data found, so “results need to be interpreted with this in mind.”

Other issues were the single-center design and relatively mild pain at baseline (mean 6.5 on a 20-point scale), which left little room for improvement, although it may have helped adherence to exercise, they added.

Whether the statistically significant differences in the trial were clinically relevant wasn’t clear for some measures like compression force and didn’t reach the threshold for a meaningful change in others, like quality of life.