Does making less money improve one’s chances of having a successful outcome from knee replacement surgery? According to a large new study, the surprising answer is yes.
Researchers at the Mayo Clinic and the University of Alabama at Birmingham say patients who made $35,000 a year or less reported less pain and better knee function two years after their surgery than wealthier people did.
“It runs counter to what many might have expected to see,” said David Lewallen, MD, an orthopedic surgeon at the Mayo Clinic and co-author of the study. “We need to work to understand it further.”
One possible explanation could be that many lower-income patients delay knee replacement as long as possible, so their knees tend to be in worse shape and their feeling of improvement after the procedure more dramatic.
Knee replacement surgery consists of replacing diseased or damaged joint surfaces with metal and plastic components shaped to allow continued motion of the knee. Researchers looked at the results of more than 7,000 patients listed in the Mayo Clinic Total Joint Registry to assess the association of income with knee function and pain as reported by patients at follow-up appointments two years after knee replacement surgery.
After adjusting for factors such as age, gender and body mass index, researchers found that patients making $35,000 or less rated their overall improvement in knee function “better” more often than those who earned more. They also were less likely to report moderate to severe pain.
What the findings mean, according to Dr. Lewallen, is that all other things being equal, a low income doesn’t necessarily mean a patient will see poorer results from knee replacement.
“This is one small piece of a very large puzzle in understanding patient outcomes following a well-defined surgery that we know is very effective for most,” said Dr. Lewallen.
The study was presented at the American College of Rheumatology annual meeting in Washington.