For people with knee osteoarthritis, or at high risk for it, a brisk walk for just 5 minutes a day can lower the risk for total knee replacement over 5 years, results from a new study show
Previous literature has been mixed on whether walking briskly is beneficial or could cause further injury in this patient population, said Hiral Master, PT, who is a Ph.D. candidate in physical therapy at the University of Delaware in Newark.
This study "is a starting point for people with knee osteoarthritis," she said here at the American College of Rheumatology 2018 Annual Meeting. And the implications for the cost of healthcare are huge. "There were 450,000 total knee replacements in 2005, and it is projected that there will be 3.4 million in 2030," she reported.
For their 5-year study, Master and her colleagues identified patients enrolled in the Osteoarthritis Initiative for 48 months who had not undergone total knee arthroplasty during that study period.
The team used data from accelerometers to classify the walking speed of study participants. Nonwalking was less than 1 step/min; very light walking was 1 to 49 steps/min; light walking, or a stroll, was 50 to 100 steps/min; and moderate to vigorous walking was more than 100 steps/min.
The average age of the study cohort was 65 years, average body mass index was 28.4 kg/m², and 55% of the participants were women. During the 5-year period, 1854 participants wore an accelerometer for at least 4 of 7 days, and 108 underwent total knee replacement.
Participants who replaced 5 minutes of nonwalking time per day with 5 minutes of walking at moderate to vigorous intensity reduced their risk for total knee replacement by 16% (hazard ratio, 0.84; 95% confidence interval, 0.72 – 0.98).
However, replacing nonwalking time with 5 minutes of very light or light walking had no effect. In addition, no differences were found between participants with radiographic knee osteoarthritis and those with symptomatic knee osteoarthritis.
"Can You Spend 5 Minutes for Your Osteoarthritis?"
These findings carry an important message that surgeons, rheumatologists, and primary care physicians should share with their patients, said Navin Fernando, MD, from the University of Washington School of Medicine in Seattle.
Patients who are more active maintain muscle conditioning and fluid production, he explained, which can support the joints and protect the cartilage. "Activity level also predicts body mass and general health, which is important in the weight that this distributed on the joints," he told Medscape Medical News. "All of these things make it plausible that the results of the study are accurate. I think it's a valuable study for anyone in patient care."
Nonpharmaceutical options are especially important in orthopedics, Fernando added, "given that a high percentage of orthopedic surgeons are responsible for prescribing narcotic medications."
Whether or not a patient ends up needing a knee replacement, walking is a good activity to undertake, he noted. And because total knee replacements only last for a limited time, any delay is helpful, said Dan White, PT, ScD, from the University of Delaware, who was senior author of the study.
"A lot of people get knee osteoarthritis at 50, and the latest stats say replacements last about 20 years. If you can delay it, that's a big deal," he explained. The brisk walking tested is not close to a run so there is little risk of injury, he added.
"Most people, if you ask them to walk 50 feet, will walk at a moderate intensity. It's not a stroll, but a purposeful walk," White said. "What we're trying to say here is that it doesn't take much. With 5 minutes a day of activity, you have a substantial reduction in your near-term risk of a joint replacement," he said. "Can you spend 5 minutes for your osteoarthritis?"
For people with severe osteoarthritis, 10 minutes of brisk walking a day is safe, said White. Although the pain might increase immediately after the walk, it will not increase over the long term, he added. Data suggesting that the benefit keeps increasing with the number of minutes of walking will be published in the future, Master told Medscape Medical News.