In a finding that surprised medical specialists, new research has found lower-income patients fare better than their wealthier peers after knee-surgery replacement.
The study, by Mayo Clinic and the University of Alabama at Birmingham researchers, indicates knee-surgery patients who make $35,000 a year or less tend to report less pain and better knee function at their two-year checkups than higher-income people.
"It runs counter to what many might have expected to see," said Dr. David Lewallen, an orthopedic surgeon at Mayo Clinic in Rochester who helped lead the study, presented at the American College of Rheumatology meeting in Washington this week. "We need to work to understand it further."
One possible explanation: Lower-income patients may delay knee replacement as long as possible, so they tend to be in worse shape at the time of surgery. As a result their feelings of improvement afterward are more dramatic, Lewallen said.
To reach their conclusions, researchers examined data from a registry of nearly all of the 100,000 joint replacements performed at Mayo Clinic over the past 43 years. After accounting for other factors that can affect knee-replacement results — such as age, gender, body mass index, and underlying diagnosis — they found lower-income patients report rated their overall improvement in knee function "better" more often than those who earned more, and were less likely to report moderate to severe pain.
"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," Lewallen said.