Effects of socioeconomic status on patients' outcome after total knee arthroplasty.

Objective: To identify whether patients in lower socioeconomic groups had worse pain and functional levels prior to total knee arthroplasty and then establish whether these patients had poorer post-operative outcomes following total knee arthroplasty.

Method: Data was obtained from a prospective observational study of 974 patients undergoing primary total knee arthroplasty for osteoarthritis. The study was undertaken in 13 centers in 4 countries. Pre-operative data was collected and patients were followed for 2 years post-operatively. Pre-operative details of the patients' demographics; socioeconomic status (SES) (education and income); height; weight and co-morbid conditions were obtained. The WOMAC scores were obtained preoperatively and during follow-up.

Results: Using multivariate linear regression analysis, patients with a lower income had a significantly worse pre-operative WOMAC Pain (P = 0.021) and function score (P = 0.039) than those with higher incomes. However, income did not have a significant impact on outcome at final follow-up after adjusting for other significant covariates. Level of education did not correlate with pre-operative scores or with outcome at any time during follow-up.

Conclusion: Across all four countries, patients with lower incomes appeared to have a greater need for total knee arthroplasty. However, level of income and educational status did not appear to affect the final outcome following total knee arthroplasty. Patients with lower incomes appeared able to compensate for their worse pre-operative score and obtain similar outcomes post-operatively. These findings are in contrast to studies on other medical conditions and surgical interventions, in which a lower SES has been found to have a negative impact on patient outcomes.