Weight Loss and Exercise Reduce Pain and Improve Physical Functioning in Overweight Postmenopausal Women with Knee OA
Studies have consistently shown that obese persons, especially obese older women, are at higher risk for knee osteoarthritis (OA). Longitudinal data from the Framingham Study indicates that a weight loss in women of as little as 11 lbs can significantly lower the risk of developing knee OA. On the basis of epidemiologic findings such as these, the American College of Rheumatology (ACR) recommends weight loss as a treatment for obese persons with knee OA. However, these are very little data from clinical trials that speak to the issue of whether or not weight loss is beneficial to pain, symptoms, and physical functioning in obese persons with knee OA.
Methods: To test the hypothesis that promoting weight reduction and walking activity would reduce knee pain and improve physical functioning, Martin et al (J Clin Rheum 7:219, 2001) had 48 overweight (body mass index [BMI: kg/m2] 25 to 29.9) and obese (BMI > 30) postmenopausal women take part in a 6-month weight loss and walking program that consisted of weekly hour long nutrition classes and 3 exercise walking sessions per week (1 exercise session per week was supervised by exercise technicians). Measures of knee pain and symptoms (Western Ontario and McMaster University Osteoarthritis Index [WOMAN]), physical function (e.g., 6-minute walk) and exercise capacity (VO2max) were taken at the start of the study and after the 6-month intervention.
Results: Sixty-three percent of the women (30/48) completed the program. The only difference between completers and non-completers was that the VO2max of the women who did not complete the trial was lower than those who completed the trial (p<.05). Among completers, 12 women were overweight at baseline and 18 were obese at baseline. The intervention produced an average weight loss of 5.6 + 4.6 kg in the 30 women who completed the trial. Compared to baseline, the women significantly improved their 6-minute walk time, as well as VO2max. Improvements on the WOMAC pain and function scores, however, were restricted only to women who were obese at baseline.
Conclusions: This uncontrolled pilot study suggests that a weight loss and walking program improves physical functioning, fitness and reduces pain and symptoms in obese postmenopausal women with symptomatic knee OA.
Editorial Comment: Overweight and obesity are established risk factors for the development of knee OA. Since body weight is a potentially modifiable risk factor, it would be useful to know whether weight loss would have beneficial effects on pain, symptoms and functional status in obese persons with established knee OA. This pilot study by Martin and colleagues offers preliminary evidence that weight reduction and walking exercise may indeed provide some benefit on pain and functioning. However, it should be noted that the benefits were relatively modest, and were generally restricted only to women who were obese, as opposed to overweight, at the start of the study. Moreover, nearly 40% of the women did not complete the trial suggesting that the program may have been too onerous and time consuming to participants. Of course, the absence of a randomized design and control group makes it impossible to definitively determine whether the intervention itself was responsible for the benefits or whether they were due simply to the effects of participating in a clinical trial that involved increased attention and social support. Larger randomized controlled trials of longer duration are required to truly establish the effects of weight reduction on knee OA. Ideally, such a trial should be designed also to determine the relative contributions and the mechanisms underlying the effects of weight loss and walking exercise on the study outcomes. Nonetheless, the results offer at least tentative support that weight loss and exercise walking may be of benefit to pain, symptoms and function in obese adults.