WebMD Medical News
Louise Chang, MD
Jan. 7, 2010 -- Compared to running barefoot, running in
conventional running shoes increases stress on the knee joints up to 38%,
according to a new study.
''There is an increase in joint torque that may be detrimental," says D.
Casey Kerrigan, MD, the lead author of the study, published in PM&R: The
Journal of Injury, Function and Rehabilitation.
Joint torque is a measure of how much a force causes the joint to
But Kerrigan is not advocating that runners take up barefoot running -- just
that her findings may be a reason to redesign running shoes. Kerrigan, formerly
chairwoman and professor of physical medicine and rehabilitation at the
University of Virginia, Charlottesville, now heads JKM Technologies and is
designing a running shoe.
At least one podiatric specialist calls the study finding ''much ado about
Kerrigan's team evaluated 68 runners -- 37 women, average age 31, and 31
men, average age 36 -- who ran at least 15 miles a week. None had
any history of musculoskeletal injury.
Participants ran barefoot on a treadmill and then in a running shoe: the
Kerrigan's team observed how each condition, barefoot and shod, affected the
joints of the hip, knee, and ankle.
Compared to running barefoot, the researchers found running in running
shoes increased stress on the lower extremities. They found a 54%
increase in the hip internal rotation torque and a 36% to 38% increase in knee
torque. Is that increase mild, moderate, worrisome? "We don't know,"
Kerrigan tells WebMD. "We just know it's an increase."
She attributes the increased stress to the characteristic design of the
majority of running shoes, including an elevated heel and increased material in
the midsole arch.
Providing this cushioning in the heel, she suspects, counteracts the body's
natural response to compensate for the torque associated with impact.
The increases found in her current study are higher than when she compared
barefoot walking to walking in high heels. The high-heel shoes increased knee
joint torque by 20% to 26%, she says.
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
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,
''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
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,"
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
So what's a runner to wear -- or not wear? "Nobody should take the message
that being barefoot is better than wearing any type of shoe whatsoever," says
Williams of the new study.
Kerrigan, too, says her research isn't a vote for the barefoot running trend
-- nor for giving up running.
"If you are happy with your running shoes, you don't necessarily have to
change them," Williams says. But if you have an injury, he suggests consulting
a sports podiatrist and getting advice about the best shoe features for
''I would suggest runners try a number of different types of shoes until
they find one that they like," Hamill says. "Also, buy two or three pairs of
shoes and rotate them each day."
SOURCES:Kerrigan, D. PM&R: The Journal of Injury, Function and
Rehabilitation, Dec. 2009; vol 1: pp 1058-1063.D. Casey Kerrigan, MD, chairwoman, JKM Technologies LLC, Charlottesvile,
Va.Joseph Hamill, PhD, professor of kinesiology and director, Biomechanics
Laboratory, University of Massachusetts, Amherst.Bruce Williams, DPM, podiatrist, Valparaiso, Ind.; past president,
American Academy of Podiatric Sports Medicine; spokesman, American Podiatric
Medical Association.Tiffany Herman, spokeswoman, Brooks Shoes.Schmitt, H. Orthopade, October 2006; vol 35: pp 1087-1092.
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