OA Pain Loss through Weight Loss

Osteoarthritis patients reported improved pain and function after weight loss

(RxWiki News) Osteoarthritis is known as the "wear and tear" form of arthritis. If you're overweight, you could be putting more strain on your joints and adding to this wear and tear. But losing weight could change that.

A recent study showed that patients with knee osteoarthritis may be able to relieve pain and improve function by losing weight.

"Lose weight to give your arthritic joints some relief."

Results showed that patients who lost at least 10 percent of their body weight reported less pain and improved knee function, compared to those who lost less weight. In contrast, patients who gained 10 percent or more of their body weight had worse pain and function.

The study showed a dose-response relationship between changes in body weight and changes in pain and function. A dose-response relationship means that patients had more improved pain and function for every unit of weight lost.

According to the authors, these results suggest that doctors should encourage their overweight arthritis patients to lose weight, and that the goal for weight loss should be 10 percent or more of body weight.

The research was conducted by Daniel L. Riddle, PT, PhD, FAPTA, of Virginia Commonwealth University, and Paul W. Stratford, DipPT, MSC, of McMaster University in Canada.

The study included 1,410 patients with knee osteoarthritis. Data came from two past studies in which patients were followed from 30 months to three years. Participants were grouped into five weight loss categories: weight loss of 10 percent or more, weight loss of 5 to 9.9 percent, weight loss of 4.9 percent to weight gain of 4.9 percent, weight gain of 5 to 9.9 percent and weight gain of 10 percent or more.

To measure pain and function, the researchers used the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for pain and function. WOMAC pain scores range from 0-20, with higher scores indicating higher levels of pain. WOMAC function scores range from 0-68, with higher scores indicating worse function.

The researchers compared WOMAC pain and function scores of patients who lost or gained 4.9 percent of body weight (reference group) to scores of those in the other weight change groups.

Among patients who gained 10 percent or more of body weight, WOMAC pain scores worsened (increased) by 1.6 points, while WOMAC physical function scores worsened (increased) by 5.4 points, compared to the reference group.

Even though these changes may seem small, the authors noted that it is important to distinguish between group-level changes and within patient changes. That is, changes in WOMAC scores between individuals may be much greater than changes in WOMAC scores between groups.

The study also showed the percentages of patients who met or exceeded important markers of improvement to pain and function. For example, 45.1 percent of patients who lost 10 percent or more of body weight reported improved function that met or exceeded WOMAC function standards (9 physical function points). In comparison, 29.2 percent of patients who lost 5 to 9.9 percent of body weight met this important marker of function. Results showed similar percentages with regards to WOMAC pain scores.

The authors pointed out some limitations to their study. First, even though the sample size was large, researchers lacked follow-up weight data on 21 percent of participants. Second, patients from the two data sets were different in several ways, but the researchers chose not to account for those differences. Finally, the study's results only showed a relationship between weight change and change in physical function and pain. In other words, the researchers could not conclude that weight loss or weight gain directly caused changes in pain and function.

"The results of our study have the potential to impact clinical practice. Clinicians should encourage patients who are overweight to lose weight, and the target magnitude of weight loss, based on our study and the NIH recommendations, should be 10 percent or more of body weight," the authors said.

In addition, doctors can inform patients about the consequences of weight gain, specifically how gaining weight can increase pain and disability. On the other hand, patients can benefit by knowing that losing weight can relieve pain and improve function, the authors concluded.

The study was published December 27 in Arthritis Care & Research. Research was supported in part by the National Institutes of Health and pharmaceutical companies Merck, Novartis, GlaxoSmithKline and Pfizer. Dr. Riddle has received fees from the Physical Therapy Editorial Board.

Review Date: 
January 10, 2013