Running Shoes Study: Analysis
Some torque on the knee is normal, of course. "What we are saying is, there is an increase over what would be experienced just walking around," Kerrigan says.
Her concern is that the excess stress may contribute to knee osteoarthritis, although the study did not look at a link between running shoes and injury or running shoes and the development of arthritis.
She isn't suggesting barefoot running -- a trend that's picked up steam in the past year or so -- is necessarily better than running in athletic shoes, she says.
Running Shoes Study: Other Opinions
''It's much ado about nothing," says Bruce Williams, DPM, past president of the American Academy of Podiatric Sports Medicine and a spokesman for the American Podiatric Medical Association, of the study results.
"She showed there was an increase in joint forces, but that's it," says Williams, a podiatrist in Valparaiso, Ind., and a runner. There was no link shown between running shoes and running injuries, nor with development of arthritis -- both beyond the scope of the study.
The bulk of research studies have found that runners don't have a higher incidence of knee osteoarthritis than the general population, Williams tells WebMD.
In one study, for instance, German researchers evaluated 20 former elite marathon runners and compared them to the general population, looking for arthritis. They found that knee osteoarthritis was rare in the former marathoners, publishing the result in the journal Orthopade.
Ideally, Kerrigan's team should have looked at many different shoe types, says Joseph Hamill, PhD, professor of kinesiology and director of the Biomechanics Laboratory at the University of Massachusetts, Amherst, who has researched the biomechanics of running shoes. "For example, a racing flat has very little in the way of cushioning and is almost like running barefoot," Hamill says.
Running Shoes Study: Industry Input
In an email response, Tiffany Herman, a spokeswoman for Brooks Sports, which makes running shoes, says: ''We value the results of this study and are in active research and development on many unique performance running footwear solutions at Brooks."
''This includes styles that enhance the natural motion of the foot and body while offering protection from weather conditions, road debris, and individual biomechanical variances."