Lower Income Tied to Less Knee Pain

Knee arthroplasty pain is less prevalent among lower income patients

/ Author:  / Reviewed by: Robert Carlson, M.D

(RxWiki News) The quality of care when getting a new knee shouldn't depend on patients' income. Treatment should be the same no matter who's under the knife. But lower income patients might feel better about their surgery than patients who earn more.

Lower income patients who had surgery to fully replace a knee reported having less pain and more mobility years after surgery than higher income patients who had the surgery, new research has shown.

The findings suggest that concerns about care quality are not warranted based on patients' income and what they earn, according to researchers.

"Ask your doctor any questions you have about surgery."

Jasvinder Singh, MBBS, MPH, from the Medicine Service and Center for Surgical Medical Acute Care Research and Transitions, led the study to find whether income was linked with pain and knee function after having total knee arthroplasty (TKA), or surgery to totally replace the knee.

Researchers looked at data from more than 7,000 knee procedures collected by the Mayo Clinic Total Joint Registry.

The included records contained information on knee function, pain level and activity limitations two years and five years after having surgery. 

Patients were divided into groups based on their income. Researchers classified those who made less than $35,000 as those with lower income. Individuals who made more than $45,000 were in the higher income group.

Lower income patients or those whose income fell between $35,000 and $45,000 had less moderate to severe pain compared to those who made more than $45,000.

The two lower income groups also reported fewer moderate to severe limitations in their ability to move.

At two years, patients with less than $35,000 annual income were twice as likely to report having slightly better knee function compared to patients with more than $45,000.

"This finding should not be surprising at all considering that those in the lower income categories have worse preoperative functional status, but similar postoperative function after TKA than those in the higher categories," researchers wrote in their report.

"Since those with a lower income have worse scores preoperatively, they have a much greater chance to improve their knee function, compared to those on a higher income," they wrote.

Five years after treatment, lower income individuals continued to function better and have less pain than those with higher income.

The authors noted a few limitations to their study. Only half the surveys were completed and returned, and income was based on a zip code's median income instead of actual personal income. 

Researchers recommended that future research investigate why patients with lower incomes have better outcomes after having a knee replaced.

The study was published March 6 in the journal BMC Medicine. The authors received research grants, consultant fees and royalties/speaker fees from a number of pharmaceutical companies. No other conflicts of interest were reported.

Reviewed by: 
Review Date: 
March 6, 2013
Last Updated:
March 17, 2013