The objective of this study was to evaluate the psychometric properties of a new patient-reported measure of knee implant functional performance associated with physical activities prior to and following primary total knee arthroplasty (TKA). The Patient’s Knee Implant Performance questionnaire (PKIP) was developed to assess factors that lead to patient dissatisfaction and describe unmet needs in knee functional performance.
The psychometric analysis sample (n=764) was based on a multicenter, prospective, noncomparative longitudinal study of patients with osteoarthritis undergoing TKA at 22 international sites. The PKIP and additional patient-reported outcomes and clinical measures were collected preoperatively, postoperatively at less than 1 year, at a minimum of 1 year, and at 2 years. The PKIP structure and its reliability, construct validity, discriminating ability, and responsiveness were assessed.
Based on inter-item correlations, factor analyses, and results of previous qualitative research, the PKIP was scored as four subscales (Stability, Confidence, Satisfaction, and Activity Modification) and an Overall PKIP score. The Overall PKIP score met reliability standards (internal consistency: alpha =0.78 at minimum 1 year; test-retest: intraclass correlation coefficient =0.77). Correlations between the PKIP and other available measures provided evidence of construct validity. For example, the PKIP correlated 0.19 and 0.50 with the American Knee Society Score preoperatively and at less than 1 year, respectively, and correlated 0.69 and 0.77, with the Knee Injury and Osteoarthritis Outcome Score Quality of Life subscale. The PKIP was capable of discriminating between groups of patients with better or worse knee functioning as defined by clinician-rated measures; hypothesis tests were in the predicted direction and mostly statistically significant. The effect size for the Overall PKIP score was 2.38, indicating that the PKIP was highly responsive.
The reliability, validity, and responsiveness of the PKIP support its use among patients undergoing primary TKA.
Psychometric evaluation of the Patient's Knee Implant Performance (PKIP) questionnaire for the assessment of primary total knee arthroplasty