Why So Idle with Knee OA?

Inactivity in osteoarthritis patients linked to obesity and other modifiable risk factors

(RxWiki News) Being obese or overweight can make osteoarthritis worse. Staying physically active is one of the best ways to avoid putting on extra pounds. However, many osteoarthritis patients remain inactive.

In a recent study, nearly half of patients with knee osteoarthritis were inactive. Findings showed that arthritis patients who were overweight or obese, had a poor diet, had severe knee pain or severely poor knee function were more likely to be inactive.

These findings suggest that there may be a serious need to improve physical activity among patients with knee osteoarthritis. According to the authors, increasing physical activity among these patients will likely involve weight management, healthy diet and improving pain and disability.

"Stay active if you have osteoarthritis."

Jungwha Lee, PhD, of Northwestern University, and colleagues looked at how obesity and other modifiable risk factors were related to physical inactivity. In other words, they wanted to see if certain lifestyle habits and characteristics of osteoarthritis were barriers to activity.

The study included 1,089 patients with knee osteoarthritis. Patients' activity was monitored using an accelerometer (a device that measures acceleration, or movement).

Results showed:

  • Patients who were overweight had 1.8 times higher odds of inactivity than those who were not overweight.
  • Patients who were obese had 3.9 times higher odds of inactivity than those who were not obese.
  • Patients who did not have enough fiber in their diet had 1.6 times higher odds of inactivity than those who ate enough fiber.
  • Patients with severe knee dysfunction had 1.9 times odds of inactivity than those with better knee function.
  • Patients with severe pain had 1.7 times higher odds of inactivity than those with less pain.

Osteoarthritis patients often worry that exercise is going to hurt their joints and cause more pain. However, many studies have shown that regular exercise can help patients maintain flexible joints, lose weight that puts a strain on joints and strengthen the muscles around joints - all of which can improve the ability to move and function.

"A low level of physical activity among adults with arthritis is a recognized public health concern," the authors wrote.

"Despite substantial health benefits related to physical activity, adults with [knee osteoarthritis] were particularly inactive," they wrote.

"There is a critical need to intensify public health efforts to reduce physical inactivity among adults with knee osteoarthritis. Being obese/overweight, the quality of the diet, severe pain, severe dysfunction and levels of physical activity are interrelated in adults with knee osteoarthritis," they said.

"One cannot hope to improve physical activity patterns in adults with knee osteoarthritis without consideration for weight management, diet and osteoarthritis pain and disability, as all may affect successful achievement of activity goals."

They concluded that all of these factors should be considered when developing physical activity plans aimed at arthritis patients with low activity levels.

The study had some limitations. First, accelerometers do not reveal the type of physical activity, which would be helpful information in designing interventions. The accelerometer used in this study did not account for water activities and could not capture all the movements involved in cycling. Second, there was limited data on radiographic (as shown by X-ray) knee joint damage and dietary information. Finally, the study did not show a causal relationship between the modifiable risk factors and inactivity. That is, the results did not show that factors like obesity or severe knee pain directly caused patients to be inactive.

The study was published December 27 in Arthritis Care & Research, a journal of the American College of Rheumatology. Research was funded by the National Institute for Arthritis and Musculoskeletal Diseases, Falk Medical Research Trust, the Osteoarthritis Initiative, Merck Research Laboratories, Novartis Pharmaceuticals, GlaxoSmithKline and Pfizer. Study co-author Dr. Charles Eaton has received honoraria (less than $10,000) from the Medical University of South Carolina.

Review Date: 
January 11, 2013