A new study finds that knee replacement surgery may
raise a person's risk of gaining weight, says a Reuters
News article based on a study published in Arthritis Care & Research.
For this study, lead investigator Daniel
Riddle, PT, PhD, FAPTA, and his group used a patient registry from the Mayo
Clinic in Rochester, Minnesota, which collected information on 917 knee
replacement patients before and after their procedures.
The researchers found that 5 years after surgery, 30% of patients had gained
at least 5% of their weight at the time of the surgery.
In contrast, fewer than 20% of those in a comparison group of similar people
who had not had surgery gained equivalent amounts of weight in the same period.
Riddle's team said that this degree of weight gain can lead to
"meaningful effects on cardiovascular and diabetes-related risk as well as
pain and function."
One possible explanation for the counter-intuitive results, experts said, is
that if people have spent years adapting to knee pain by taking it easy, they
don't automatically change their habits when the pain is reduced, reports
"After knee replacement we get them stronger and moving better, but
they don't seem to take advantage of the functional gains," said Joseph
Zeni, PT, PhD, a physical therapy professor at the University of Delaware, who
was not part of the study. "I think that has to do with the fact that we
don't address the behavioral modifications that have happened during the course
of arthritis before the surgery."
Part of the explanation for the weight gain could be the age at which
patients get surgery. People in their 50s and 60s tend to gain weight, anyway.
Still, in light of the lower rates of weight gain in the comparison group,
which was also middle aged and older, Riddle said something else may also be at
In fact, the team found that patients who had lost weight before their
surgery were slightly more likely to gain weight afterwards—perhaps because
when people lose weight in anticipation of an event, such as surgery, they are
more likely to put it back on after they're achieved the goal, says the
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