Traditional assessment of health outcome following total knee arthroplasty was confounded by response shift phenomenon

J Clin Epidemiol. 2009 Jan;62(1):91-6. doi: 10.1016/j.jclinepi.2008.08.004.


Objectives: To examine the existence, direction, and effect of response shift as measured by the total score of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and SF-36 physical and mental component score domains at 6 months and 1 year after primary total knee arthroplasty (TKA).

Study design and setting: Consecutive candidates participated in the study. In line with the Then-test design, two sets of questionnaires were completed at 6 months and 1 year postoperatively. Patients were divided into three groups on the basis of minimal clinically important differences (MCIDs). Parametric and nonparametric statistics and generalized mixed effects models were used.

Results: Two hundred and thirty-six patients completed the study. The magnitude of response shift increased over time for SF-36 physical and mental component scores. The traditional unadjusted presurgical and 1-year postsurgical assessment failed to reveal any mental health improvement, whereas the adjusted treatment effect demonstrated statistically significant changes.

Conclusion: Response shift phenomenon increases with time in patients undergoing orthopedic interventions. The traditional pre- and post-assessment of joint replacement surgery may be confounded by a change in perspective and in internal standards of measurement in patients undergoing surgery. Response shift has substantial impact on measuring recovery in this population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Psychological
  • Aged
  • Arthroplasty, Replacement, Knee / psychology*
  • Arthroplasty, Replacement, Knee / rehabilitation
  • Bias
  • Female
  • Health Status
  • Humans
  • Male
  • Middle Aged
  • Ontario
  • Outcome Assessment, Health Care / standards*
  • Postoperative Period
  • Quality of Life / psychology
  • Statistics, Nonparametric
  • Surveys and Questionnaires
  • Treatment Outcome