Published: Sep 24, 2013
By Crystal Phend, Senior Staff Writer, MedPage Today

Full Story:  http://www.medpagetoday.com/Orthopedics/Orthopedics/41832

Action Points

• Note that this randomized trial demonstrated that subjective knee osteoarthritis measures improved more among subjects in the diet and exercise arm than in the diet alone or exercise alone arm.
• Be aware that objective measures of loading and inflammation demonstrated the favorable effect of diet, without a synergistic effect of added exercise.

Diet and exercise eased knee osteoarthritis better than either alone for overweight and obese patients, a clinical trial showed.

Joint inflammation, pain, function, and quality of life all significantly favored the combined approach compared with exercise alone over 18 months, Stephen P. Messier, PhD, of Wake Forest University in Winston-Salem, N.C., and colleagues found.

Comparing single strategies, diet came out better than exercise for reducing knee joint loading and cutting inflammation, the group reported in the Sept. 25 issue of theJournal of the American Medical Association.

All told, the mean weight loss was 11.4% of body weight in the combined diet and exercise group compared with 9.5% in the diet-alone group and 2% in the exercise-alone group (P<0.001 for both diet groups versus exercise alone).

All three strategies had a target of 10% 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).

Although this means perhaps a lack of generalizability to routine clinical practice where no such support is typically available, it does show what’s possible, commented Amanda E. Nelson, MD, MSCR, a rhematologist at the University of North Carolina at Chapel Hill.

“This gives us some real guidelines for what kind of change needs to happen to be meaningful,” she told MedPage Today. “So we can tell patients if they’re going to lose 10% 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.”

What isn’t clear is if it matters how patients achieve the weight loss — if types of exercise other than the prescribed routine of aerobics and strength training used in the trial or different diets could 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 stuck it out to month 18 (88%).

All patients had a sedentary lifestyle to start with. They were randomized to one of three open-label interventions:

• Intensive weight loss with meal replacement shakes, substantial caloric restriction (800 to 1,000 kcal per day below intake), weekly or biweekly nutrition education and behavioral group sessions, and periodic individual support sessions
• An aerobic and strength training exercise intervention for 1 hour 3 days a week, initially at a center then with the option for a home-based regimen
• Both diet and exercise interventions

Any patient who had trouble reaching the 10% body weight loss target got 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% decline in the exercise group, a 10% drop in the diet group, and a 9% 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 came out 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 were also 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.

The researchers cautioned that the study was powered to detect a greater impact on knee joint loading and inflammation than were 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.