NEW YORK (Reuters Health) - People with arthritis of the knee seem to find walking a relatively long distance less painful if they put shock absorbing insoles in their shoes, according to results of a study reported at the annual meeting of the American College of Sports Medicine in Indianapolis.

"My motivation for doing this study is that a lot of people spend a lot of money on insoles, and in people with knee osteoarthritis there is really very little evidence that they work. It hasn't been researched," Judy Foxworth, a physical therapist at North Carolina's Winston Salem State University, noted in a telephone interview with Reuters Health.

Foxworth tested the effect on knee pain of putting relatively cheap ($20) off-the-shelf shock absorbing insoles inside the shoes of 60 seniors with painful knee arthritis.

"I had people walk at their regular pace, at a fast pace, and then I had them walk for 6 minutes covering as much ground as possible in those 6 minutes. I had them rate their knee pain while they did those activities while wearing shock absorbing insoles and then while not wearing them," she explained.

The study subjects reported significantly less knee pain after walking 6 minutes while wearing the shock absorbing insoles as compared to walking 6 minutes without the insoles, Foxworth found. There were no differences in pain when walking at a regular pace or fast pace with or without the insoles.

Foxworth said that she's not sure exactly how shock absorbing insoles reduce pain. "People reported a decrease in pain but I could not explain it biomechanically, so that puts in question the efficacy of recommending these," she said.

"I looked at gait mechanics using sophisticated equipment and all of the things that I looked at, there were no differences between wearing the insoles and not wearing them while walking," she added.

"I really thought I'd see a difference in the kinetic variables -- the ground reaction forces. I thought the shock absorbing insoles would absorb more shock and there would be less force on the knee, and that's not what we found," Foxworth explained.

Nonetheless, she said, the most important thing is to be active. "So if putting shock absorbing insoles in your shoes makes you feel better and allows you to be more active, by all means use them."