A new study suggests that the risk of middle-aged and older adults developing knee arthritis is unaffected by doing up to 150 minutes per week of moderate physical activity, the level recommended by the US goverment.
Researchers from the University of North Carolina (UNC) and the Centers for Disease Control and Prevention (CDC), came to this conclusion after studying data on over 1,500 participants aged 45 and over.
The study was published online on August 27th in Arthritis Care & Research.
Lead author Dr. Kamil Barbour, who is with the CDC's Arthritis Program in the Division of Population Health, says moderate physical activity is that which results in a raised heart rate or breathing.
Examples include brisk walking, ballroom dancing, conditioning exercises, or even general housework, gardening and yard work.
Dr. Barbour says:
Knee arthritis leading cause of disability and joint pain
Osteoarthritis occurs when the cartilage and underlying bone in a joint break down, leading to bony overgrowth, pain, swelling and stiffness.
The joints most affected are the knees, hips and those of the hands and spine. The condition, for which there is currently no cure, develops gradually, usually in the over-40s.
In their background information, the authors confirm how knee osteoarthritis is a leading cause of disability and joint pain in the US, and they say that while other risk factors have been identified, the effect of physical activity is not very clear.
Physical activity guidelines and risk of knee arthritis
For their study, the researchers analyzed participant data collected between 1999 and 2010 in UNC's long-running Johnston County Osteoarthritis Project.
The project is a prospective, population-based study of knee, hip, hand and spine osteoarthritis and disability, and it is funded by the CDC and the National Institute of Arthritis, Musculoskeletal, and Skin Diseases (NIAMS).
The study data covers 1,522 African Americans and Caucasians, aged 45 years and older, who were followed for around 6 years.
The purpose of the new analysis was to see if there were any links between meeting the Department of Health and Human Services' recommended 150 minutes of moderate exercise per week and the development of knee osteoarthritis, as confirmed both by X-rays and the presence of knee pain or other symptoms.
The results showed that for participants aged 45 and over who did up to 150 minutes a week of moderate physical activity, there was no increased risk of developing knee osteoarthritis.
Participants who exercised at a higher level, up to 5 hours a week, had a slightly higher risk of developing knee osteoarthritis, but the researchers found the difference was not statistically significant.
Senior author Dr. Joanne Jordan, director of the Thurston Arthritis Research Center at the University of North Carolina School of Medicine, describes the findings as good news:
Written by Catharine Paddock PhD
"This study shows that engaging in physical activity at these levels is not going to put you at a greater risk of knee osteoarthritis. Furthermore, we found this held true no matter what a person's race, sex or body weight is. There was absolutely no association between these factors and a person's risk."