The idea made so much sense that it was rarely questioned: exercise to strengthen muscles around the knee helps patients with osteoarthritis, making it easier and less painful to move the inflamed joint.
Nearly 40 percent of Americans over age 65 have knee osteoarthritis, and tens of millions of patients have been instructed to do these exercises. Indeed, the American College of Rheumatology and the Arthritis Foundation routinely advise strength training to improve symptoms.
Stephen Messier, a professor of biomechanics at Wake Forest University, believed in the guidance. But he decided to put the prescription to the test in a rigorous 18-month clinical trial involving 377 participants. The verdict appeared in a study published this week in JAMA: Strength training did not seem to help knee pain.
One group lifted heavy weights three times a week, while another group tried moderate strength training. A third group was counseled on “healthy living” and given instructions on foot care, nutrition, managing medications and better sleep practices.
Dr. Messier had expected that the group performing the heavy lifting would fare best and that the participants who received only counseling would see no improvement in knee pain. But the outcomes were the same in all three groups. Everyone reported slightly less pain, including those who had received only counseling.
You might expect some easing in pain in the patients who exercised. But why would those who didn’t exercise also report an improvement? “It’s an interesting dilemma we’ve been put in,” Dr. Messier said.
A simple placebo effect might explain why they felt better, he said. Or it could be something scientists call a regression to the mean: Arthritis symptoms tend to surge and subside, and people tend to seek out treatments when the pain is at its peak. When it declines, as it would have anyway, they ascribe the improvement to the treatment.
“The natural history of osteoarthritis of the knee includes waxing and waning of symptoms,” said Dr. Adolph Yates, vice chair of orthopedic surgery at the University of Pittsburgh School of Medicine, who was not associated with the study. “It is what makes studying osteoarthritis of the knee interventions difficult.”
Dr. David Felson, a professor of medicine at Boston University, argued that the study did not find strength training was useless. But instead, the trial showed that very aggressive strength training was not helpful and might actually be harmful, he said, especially if the arthritic knees are bowed inward or outward, as is common.
Strong muscles can act like a vise, putting pressure on tiny areas of the knee that bear most of the load when we’re walking. When Dr. Felson scrutinized the study’s data, he saw signs that the high-intensity group experienced slightly more pain and worse functioning.
Patients tend to resist advice to exercise at all, said Dr. Robert Marx, a professor of orthopedic surgery at Weill Cornell Medical College in New York City: “They want a reason not to exercise, asking: ‘Will it make my arthritis better? Will it make my X-rays better?’”