October 4, 2023

The idea made so much sense that it’s rarely been questioned: exercise to strengthen the muscles around the knee will help patients with osteoarthritis and make moving the inflamed joint easier and less painful.

Nearly 40 percent of Americans over 65 have knee osteoarthritis, and tens of millions of patients have been instructed to do these exercises. In fact, the American College of Rheumatology and the Arthritis Foundation recommend weight training regularly to improve symptoms.

Stephen Messier, professor of biomechanics at Wake Forest University, believed in the guidance. However, he decided to test the recipe in a rigorous 18-month clinical trial with 377 participants. The verdict appeared in a study published in JAMA this week: Weight training didn’t appear to relieve knee pain.

One group lifted heavy weights three times a week while another group tried moderate strength training. A third group received “healthy living” counseling and instruction on foot care, nutrition, medication, and better sleep practices.

Dr. Messier had expected that the group doing the heavy lifting would do the best and that those participants who received advice only would see no improvement in knee pain. However, the results were the same in all three groups. All reported a little less pain, even those who only received advice.

Some pain relief can be expected in the exercising patient. But why should those who haven’t trained also report improvement? “It’s an interesting dilemma we’ve gotten into,” said Dr. Messier.

A simple placebo effect could explain why they felt better, he said. Or it could be something that scientists call regression of the mean: arthritis symptoms tend to fluctuate and subside, and people tend to seek treatments when the pain peaks. If it decreases, as it would have been anyway, they attribute the improvement to the treatment.

“The natural history of osteoarthritis of the knee includes the growth and decrease of symptoms,” said Dr. Adolph Yates, vice chairman of orthopedic surgery at the University of Pittsburgh Medical School, unrelated to the study. “It is what makes the study of osteoarthritis knee interventions difficult.”

Dr. David Felson, professor of medicine at Boston University, argued that the study did not find any strength training to be useless. Instead, the trial showed that very aggressive weight training wasn’t helpful and could actually be harmful, he said, especially if the arthritic knees are bent in or out as usual.

Strong muscles can act like a vise, putting pressure on tiny areas of the knee that carry most of the load while walking. When Dr. Felson looked at the study data, he saw evidence that the high-intensity group had slightly more pain and poorer function.

Patients tend to resist the advice to exercise at all, said Dr. Robert Marx, Professor of Orthopedic Surgery at Weill Cornell Medical College in New York City: “You want a reason not to exercise and you asked, ‘Will it improve my arthritis? Will it improve my x-rays? ‘”

He tells them that the answer to their questions is no, but that exercise stabilizes the joints. While it’s not as effective for pain as anti-inflammatory drugs, “it’s a piece of arthritis treatment.”

For Dr. Messier, who has researched arthritis and exercise for over 30 years, the new findings are a bit of a departure. His first study, published in JAMA in 1997, found that exercise groups ended up having less pain than the control group, but that wasn’t really because the participants improved. It was because those in the control group got worse.

He also noted that half of the participants in his study were overweight or obese. “What if we added weight loss to the workout?” he asked.

He tried this in another study published in JAMA in 2013, which showed that a combination of weight loss and exercise provided more pain relief than either alone.

But he had long wondered if the intensity of the strength training was important. In previous studies, participants had used weights that lagged far behind what they could actually lift. The studies only lasted six to 24 weeks, and the patients showed only modest improvements in pain and function.

Despite the new, unexpected results, Dr. Messier still encourages patients to exercise, saying that doing so can prevent an inevitable decline in muscle strength and mobility. But now it seems clear that strength training with heavy weights offers no particular benefit, rather than a moderate intensity routine with more reps and lighter weights.

Arthritis is a chronic degenerative disease of the entire joint. “It’s busy,” said Dr. Messier. “It’s not just cartilage deterioration.”

But, he added, he believes the best non-pharmaceutical intervention for knee arthritis pain is 10 percent weight loss and moderate exercise.

Dr. Messier now plans to have his next study combine weight loss with exercise in people at risk for knee osteoarthritis in the hopes of preventing this debilitating disease from occurring.