Psychometric Evaluation of the Patient's Knee Implant Performance Questionnaire.

OBJECTIVES: To evaluate the psychometric properties of Patient's Knee Implant Performance Questionnaire (PKIP), a new patient-reported measure of knee implant functional performance assessing patient experiences before and after primary total knee arthroplasty (TKA).

METHODS: The psychometric analysis sample (n = 761) was based on an ongoing, multisite, prospective, noncomparative, longitudinal study of patients undergoing TKA. The PKIP was completed at three study visits: presurgery (visit 1), less than 1 year (visit 3, days 1-303), and minimum 1 year (visit 4, days 304-668). Visit 2 was an operative visit. Supporting outcome measures were collected at each study visit. The PKIP structure and its psychometric properties were assessed as part of a secondary data analysis using an interim data cut before the end of the clinical trial.

RESULTS: The PKIP includes four subscales (confidence, stability, activity modification, and satisfaction) and an overall PKIP score. The overall PKIP score met internal consistency (visit 4 = 0.79) and test-retest reliability (intraclass correlation coefficient = 0.77) standards. Correlations between the PKIP and other measures (e.g., the American Knee Society score and the Knee Injury and Osteoarthritis Outcome Score) provided evidence of construct validity. The PKIP was capable of discriminating between groups of patients with better or worse knee function. The effect size for the overall PKIP score was 2.96 from baseline to visit 4, indicating that the PKIP was highly responsive.

CONCLUSIONS: The reliability, validity, and responsiveness of the PKIP support its use among patients undergoing TKA.