Joseph Zeni and Lynn Snyder-Mackler in the University of Delaware (UD) Department of Physical Therapy 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 over six kg in two years.
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,  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 (6.35 kg).”
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 rethink the component after total knee surgery and of patients not being in a routine of moving around,” says Snyder-Mackler, professor of physical therapy at UD, according to its release.
These findings appeared in the January online edition of Osteoarthritis and Cartilage.