The Impact of Weight Loss on Osteoarthritis of the Knee
July 13, 2005
Losing a Pound Results in a 4-Pound Reduction in Knee-Joint
Load For Each Step, Suggests Study of Overweight and
Obese Patients -
The leading cause of disability in the United States,
osteoarthritis (OA) is a complex, degenerative joint
disease with several established risk factors. For OA
of the knee, the most important modifiable risk factor
is obesity. Both the American College of Rheumatology
and the European League Against Rheumatism recommend
weight loss and exercise
to reduce the painful and incapacitating symptoms of
knee OA.
As part of a long-term study of the effects of diet
and exercise on knee OA, researchers at Wake Forest
University found that an average weight loss of 5 percent
in overweight and obese older patients brought an 18
percent gain in overall function. Drawing from that
study population, the researchers set out to investigate
the specific, direct relationship between weight loss
and knee-joint stress while walking. Featured in the
July 2005 issue of Arthritis & Rheumatism ( http://www.interscience.wiley.com/journal/arthritis),
their findings indicate that moderate weight loss results
in knee-joint load reduction of a cumulative amount
with considerable clinical implications.
Conducted over an 18-month period, the study focused
on 142 overweight and obese adults with radiographic
evidence of knee OA. Ranging in age from 60 to 89, the
subjects were mostly female (74 percent) and white (75
percent); all were considered sedentary. Each subject's
weight and body mass index (BMI), as well as scores
on standard scales of function and pain, were obtained
at baseline and again at 6-months and at 18-months.
At baseline and both follow-up visits, each subject
also underwent gait analysis and a battery of biomechanical
tests to assess changes in knee-joint forces, both compressive
and resultant, and moments, both abduction and rotation.
Over the course of the study, all participants followed
a prescribed weight loss plan, some through diet only,
some through exercise only, and some through a combination
of healthy living habits.
At the study's culmination, participants lost an average
of 2 percent of their weight and lowered their BMI by
3 percent. After adjusting for baseline body mass and
baseline knee-joint force, researchers found a significant
association between weight loss and reduction in compressive
knee-joint loads. In fact, the force reduction was 4-times
greater than the actual weight reduction. In other words,
their findings indicated that, for every 1 pound of
weight lost, there is a 4-pound reduction in the load
exerted on the knee for each step taken during daily
activities.
“The accumulated reduction in knee load for a
1-pound loss in weight would be more than 4,800 pounds
per mile walked,” notes Stephen P. Messier, Ph.D.,
the leading author of the study. “For people losing
10 pounds, each knee would be subjected to 48,000 pounds
less in compressive load per mile walked. Although there
are no longitudinal studies indicating that weight loss
in humans slows the progression of knee OA, a reduction
of this magnitude would appear to be clinically relevant.”
Supporting the positive impact of weight
loss on knee OA, this compelling study suggests
the need for further research into the potential of
weight loss-whether achieved through diet alone or in
tandem with exercise-to slow, and perhaps even prevent,
the crippling outcome of a disease too common among
older Americans.
Source: http://www.medicalnewstoday.com
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