title: The influence of income and race on total knee arthroplasty in the United States.
abstract: BACKGROUND
  The associations among income, total knee arthroplasty, and underlying rates of knee osteoarthritis are not well understood. We studied whether high-income Medicare recipients are more likely to have a knee arthroplasty and less likely to suffer from knee osteoarthritis.
  
  
  METHODS
  Two data sources were used: (1) the 2000 United States Medicare claims data measuring the incidence of total knee arthroplasty by race, ethnicity, zip (postal) code income, and region (n = 27.5 million) and (2) the National Health and Nutrition Examination Survey (NHANES III) for individuals with an age of sixty years or more (n = 1926) with radiographic and clinical evidence of osteoarthritis. Logistic regression methods were used to adjust for covariates.
  
  
  RESULTS
  At the national level, age-adjusted rates of total knee arthroplasty in the high-income quintile were no higher than those in the low-income group (odds ratio, 0.98; 95% confidence interval, 0.96 to 1.00). Within regions, access to care was better for high-income groups (odds ratio, 1.19; 95% confidence interval, 1.17 to 1.22). Racial disparities in arthroplasty were significant (p < 0.001); the odds ratio was 0.36 (95% confidence interval, 0.34 to 0.38) for black men and 0.45 (95% confidence interval, 0.41 to 0.49) for Asian women. There was no evidence of an income gradient for most clinical and radiographic measures of arthritis. The exception was a significant negative association between income and pain on passive motion (p < 0.05).
  
  
  CONCLUSIONS
  High-income Medicare enrollees are no less likely to have osteoarthritis than low-income enrollees but have somewhat better access to care. Racial disparities are more important than those that are attributable to socioeconomic status.
authors.affiliation: Center for Evaluative Clinical Sciences, HB 7152 Dartmouth Medical School, Hanover, NH 03755, USA. jon.skinner@dartmouth.edu
authors.forename: Jonathan
authors.initials: J
authors.lastname: Skinner
authors.forename: Weiping
authors.initials: W
authors.lastname: Zhou
authors.forename: James
authors.initials: J
authors.lastname: Weinstein
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006297:Health Services Accessibility; D006801:Humans; D007182:Income; D008297:Male; D006278:Medicare; D009749:Nutrition Surveys; D020370:Osteoarthritis, Knee / Q000208:ethnology* / Q000601:surgery; D017678:Sex Distribution; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data*