You'd think folks who’ve had knee replacement surgery and are now 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 see 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 of Osteoarthritis and Cartilage, the official journal of the Osteoarthritis Research Society International.
“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 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 re-training 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.