New research examines the benefits of physical activity, such as brisk walking, on mobility and the ability to perform daily tasks among seniors living with knee osteoarthritis.

Osteoarthritis is the most common form of arthritis among seniors in the United States. Osteoarthritis of the knee, in particular, affects 10%–13% of people aged 60 or above, and this rises as high as 40% among people older than 70.

There is currently no cure, and treatment often consists of painkillers or knee surgery, depending on how advanced the disease is. According to some estimates, for about 2 in 5 people with symptomatic knee osteoarthritis, the condition significantly interferes with their daily lives.

New research, which appears in the American Journal of Preventive Medicine, examines the effects of physical activity on disability induced by knee osteoarthritis. Dorothy Dunlop, PhD, a professor of preventive medicine at the Northwestern University Feinberg School of Medicine, in Chicago, IL, is the lead author of the research.

Walking lowers disability risk by 85%

Dunlop and colleagues analyzed data from over 1,500 adults whose medical information had been collected as part of the national Osteoarthritis Initiative. The participants all lived with osteoarthritis and experienced pain, aches, and stiffness in their lower extremities as a result. However, they did not have any disability when they started the study.

The researchers used accelerometers to monitor the participants' physical activity and follow them clinically for a period of 4 years. "Our goal was to see what kind of activity would help people remain free of disability," explains Dunlop.

The analysis revealed that 1 weekly hour of moderate-to-vigorous physical activity helped the participants maintain standard levels of physical ability. Participants who got at least this much physical activity had, for instance, no trouble performing daily tasks, such as getting dressed, bathing, walking across the room, or crossing the street swiftly and safely.

More specifically, a weekly hour of exercise lowered the risk of mobility-related disability by 85% and that of daily living disability by nearly 45%. For the participants, an activity such as brisk walking counted as moderate-to-vigorous exercise.

By the end of the study period, 24% of the seniors who did not engage in a weekly hour of exercise walked so slowly that they could not cross the street before the traffic lights changed, and 23% said that they had trouble performing their regular morning tasks.

Guidelines may need changing

According to current government guidelines, all seniors should engage in at least 2.5 hours of moderate-intensity physical activity every week to reduce the risk of chronic disease. But such a level of physical activity may be harder to achieve for people who are inactive due to lower extremity pain, says Dunlop.

"We hope this new public health finding will motivate an intermediate physical activity goal," she explains. "One hour a week is a stepping stone for people who are currently inactive. People can start to work toward that."

"This is less than 10 minutes a day for people to maintain their independence. It's very doable. This minimum threshold may motivate inactive older adults to begin their path toward a physically active lifestyle with the wide range of health benefits promoted by physical activity."

—Dorothy Dunlop, PhD