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People with osteoarthritis (OA) of the knee who got no benefit from an exercise program blamed their other problems with health and life in general for the lack of response, researchers said.

In interviews conducted with responders and nonresponders in a randomized trial, those seeing no improvement in pain or function in the program cited their excess body weight, comorbidities, and interference from "life events" as preventing them from following the exercise regimen adequately, according to Rana Hinman, BPhysio, PhD, of the University of Melbourne in Australia, and colleagues.

"Our findings may guide researchers and clinicians to better identify patients at risk of nonresponse to exercise therapy and to consider strategies to optimize outcomes for this subgroup," the researchers .

The study was meant to shed light on one of the biggest conundrums in knee OA management: why doesn't everyone obtain pain relief and improved mobility with exercise regimens that should strengthen their leg muscles and take strain off the affected joints?

"Indeed, our own clinical trials in people with knee OA who underwent physiotherapist-supported strengthening exercise and physical activity show that only 40%-60% of participants reported global improvements in pain and physical function immediately after intervention," Hinman and colleagues explained. "It is not clear why some people with knee OA 'respond' to exercise while others do not." However, the researchers added, "barriers to exercise participation" that result in patients not actually performing the activities are one potential reason.

For the current study, Hinman's group conducted semi-structured individual discussions with participants in , in which patients were randomized to receive exercise consultation and coaching either through videos or in person over a 3-month period. The researchers approached 16 responders (those reporting less pain and better function after 9 months, from both trial arms) and 24 nonresponders; 12 and 14, respectively, agreed to the interviews.

These discussions were aimed at eliciting participants' "perceptions about why they did/did not respond to the exercise intervention, including beliefs about OA and exercise, mood, and psychological factors," the investigators explained. The discussions were conducted a mean of 7 weeks after the 9-month evaluation of trial outcomes, and participants' answers were categorized qualitatively into various themes as often done in sociological research.

Participants ranged in age from mid-40s to early 80s, and about 60% were women. Nearly all were overweight or obese, among responders and nonresponders alike. The vast majority also had comorbidities, but these were primarily back pain among responders, while nonresponders reported a wider variety including hypertension, cancer, and depression.

Some nonresponders took issue with the trial's outcomes evaluations as contributing to the lack of apparent benefit from the exercise regimen. Participants had completed questionnaires periodically about pain and functional limitations. As one of the participants told the researchers, "when you do a survey, questions are always limited in terms of how you can answer them because of the way they're worded ... they've been worded for a particular answer, and you can't always give that answer."

Said another, "But if I'm having to mow a lawn, lift a lawnmower into a car, which I did and ended up with two bulging discs in my back, you're not doing the survey justice at those points in time."

But primarily the nonresponders described problems with doing the recommended exercises on schedule.

"I thought it was doing me OK but then no, I just couldn't deal with it anymore," one woman recounted. "I ended up having to have injections in my hips afterwards. Because I do have bursitis in my hips, so it actually created more problems for me."

Another woman said her comorbidities were the biggest barrier: "my general health with my hips and my back and that were the major contributor for me easing up and not doing as much as I should have been."

A man described a drop-off in adherence over time, such that in his final session, he did "hardly anything," even though he also admitted that earlier, when he was following the protocol closely, he felt it was helping.

Obesity was another reason cited for the lack of benefit. "I think if I lost 20 kilos, which should be my ultimate game, maybe 30, I suspect my knees would improve out of sight. And I mean, I lost 10 kilos and actually after losing 10, my knees did feel a bit better. So if I lost another 20, I probably think they'd be a lot better," one participant said.

And some were pessimistic about gaining any relief in the first place. "I just think osteoarthritis is just a part of life," one stated. "It's incurable, if that's the word, and you've got to live with it and therefore manage it."

Hinman and colleagues acknowledged that these results aren't the last word on reasons for nonresponse to exercise in knee OA. "[Our] findings are hypothesis-generating and should be tested in [randomized trials] by evaluating moderators (e.g., presence of comorbidities, overweight/obesity) of exercise effects," the team noted.

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