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Most patients gain weight after getting a
new knee
Newswise — You'd think folks who've had knee
replacement surgery -- finally able to walk
and exercise without pain -- would lose
weight instead of put on pounds, but
surprisingly that's not the case, according
to a University of Delaware study.
Researchers Joseph Zeni and Lynn Snyder-Mackler
in the Department of Physical Therapy in
UD's College of Health Sciences found that
patients typically drop weight in the first
few weeks after total knee arthroplasty (TKA),
but then the number on the scale starts
creeping upward, with an average weight gain
of 14 pounds in two years.
The study, which was sponsored by the
National Institutes of Health, is reported
in the Jan. 15 online edition ofOsteoarthritis
and Cartilage, the official journal of
the Osteoarthritis Research Society
International.
The research involved 106 individuals with
end-stage osteoarthritis who had knee
replacement surgery, and an age-matched,
healthy control group of 31 subjects who did
not have surgery. Height, weight, quadriceps
strength, and self-perceived functional
ability were measured during an initial
visit to UD's Physical Therapy Clinic, and
at a follow-up visit two years later.
“We saw a significant increase in body mass
index (BMI) over two years for the surgical
group, but not the control group,” says Zeni,
a research assistant professor at UD.
“Sixty-six percent of the people in the
surgical group gained weight over the two
years -- the average weight gain was 14
pounds.”
Those who had the knee replacement surgery
started out heavier and ended heavier than
the control group. The weaker the surgery
patients were, as measured by the strength
of the quadriceps, the more weight they
gained, Zeni notes.
“These findings are making us re-think the
component after total knee surgery and of
patients not being in a routine of moving
around,” says Snyder-Mackler, Alumni
Distinguished Professor of Physical Therapy
at UD.
She notes that it's critical that people not
wait too long to have a knee replaced
because their functional level going into
surgery typically dictates their functional
level after surgery.
Gaining weight after one knee replacement is
worrisome because it could jeopardize the
patient's other knee. Between 35-50 percent
will have surgery on the other side within
10 years, Snyder-Mackler says.
The researchers note that weight gain after
a knee replacement needs to be treated as a
separate concern and integrated into
post-operative care through a combination of
approaches, including nutritional counseling
to help patients with portion control, and
more emphasis on retraining patients with
new knees to walk normally.
“For physical therapists and surgeons, the
common thinking is that after a patient's
knee has been replaced, that patient will be
more active,” says Snyder-Mackler. “But the
practices and habits these patients
developed to get around in the years prior
to surgery are hard to break, and often they
don't take advantage of the functional gain
once they get a new knee,” she notes.
“We need to re-train patients with new knees
to walk more normally and more
systematically. And we need to encourage
more community participation,” Snyder-Mackler
adds. “If you're not getting out of the
house, you won't gain the benefit. We need
people with new knees to get out there --
with the help of their family, their
friends, and the community at large.”
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