VIENNA — Obese individuals with knee osteoarthritis who successfully lose 11% of their body weight and keep it off for a year can reasonably expect a 20% improvement in knee symptom scores, Robin Christensen reported at the annual European Congress of Rheumatology.
This is a moderate to large treatment effect. Clinically, it's as good as or better than can be achieved with current drug therapy—and without the side effects, said Mr. Christensen of Frederiksberg Hospital, Copenhagen.
He presented a 1-year randomized trial in which 89 obese patients with knee osteoarthritis were assigned to an intensive dietary intervention featuring weekly counseling sessions, with an emphasis upon a low-energy diet, or to a control group that got standard dietary counseling on four occasions during the year. Patients averaged 63 years of age, with a mean baseline body mass index of 36 kg/m
At year's end, the intervention group had lost a mean of 10.9 kg, or 11% of baseline weight, while controls lost 3.3 kg, or 3%. Overall, 55% in the intervention arm and 9% of controls managed to sustain at least a 10% weight loss.
The key study finding: Patients in the intensive-diet arm experienced a mean 20% reduction in their total Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores from a baseline of 936, while there was no significant change in WOMAC scores in the control group. Mr. Christensen and his coworkers calculated that for each 1% reduction in body weight maintained for a year, WOMAC scores improved by at least 15 points.
This yearlong study follows an earlier 8-week randomized trial by the same Danish investigators, in which they showed that more than one in four obese patients with knee osteoarthritis randomized to an intensive 8-week weight loss program experienced at least a 50% improvement in WOMAC scores. (Osteoarthr. Cartil. 2005;13:20–7).
The new trial was undertaken to learn if weight loss and the resultant improvement in osteoarthritis could be maintained long-term, Mr. Christensen said at the meeting, sponsored by the European League Against Rheumatism.
In a separate presentation, Stefan Lohmander, M.D., observed that while there is good epidemiologic evidence to suggest even fairly modest changes in body weight have a dramatic influence on knee osteoarthritis, only within the past year have confirmatory randomized interventional trial data become available. The evidence has been provided by the Danish group as well as by a study from Wake Forest University which concluded a diet-plus-exercise regimen was more effective than either alone (Arthritis Rheum. 2004;50:1501–10).
Sustained weight loss, while often a daunting challenge, will be perceived by many patients as an increasingly attractive therapeutic alternative in light of all the recent turbulence surrounding the nonsteroidal anti-inflammatory agents, the pharmacologic mainstay in osteoarthritis therapy, predicted Dr. Lohmander, professor of orthopedics at Lund (Sweden) University.
Two theories have been proposed to explain the association between obesity and knee osteoarthritis. One is biomechanical; it holds that obesity causes repetitive loading at the knee joint which eventually exceeds the joint's load-bearing capacity and causes symptomatic osteoarthritis.
The other explanation focuses upon metabolic factors. It's known, for example, that one-third of circulating interleukin-6, an inflammatory cytokine important in rheumatologic diseases, is secreted by fat cells. Moreover, cartilage cells are known to be insulin sensitive, and it's possible insulin resistance impairs their function. Dietary weight loss has been shown to result in reductions in a number of inflammatory markers elevated in osteoarthritis, he observed.