Development and Validation of a New Evaluation System for Patients With a Floor-based Lifestyle: The Korean Knee Score

Patients' perspectives on functioning and health have been increasingly recognized as a crucial aspect of health care, leading to the use of patient-reported instruments for outcome assessment. However, available instruments for total knee arthroplasty do not reflect the floor-based lifestyle with high knee flexion of eastern Asia. We therefore (1) describe a novel patient-generated knee evaluation instrument, the Korean knee score (KKS), to reflect floor-based lifestyles with high knee flexion that included questions regarding health-related quality of life; (2) determined the reliability of the questionnaire; and (3) performed limited validation studies. The KKS was developed by a committee of 10 experts from 10 institutes nationwide. The development procedure comprised a development phase for generation of the questionnaire and a testing phase for assessment of measurement properties: reliability, validity, and responsiveness. A total of 634 patients participated in this test survey. The KKS exhibited an intraclass correlation coefficient of 0.931 and internal consistency (Cronbach's alpha = 0.973). The absence of a ceiling or floor effect suggested content validity. The correlation coefficient with Knee Society score (knee score, function score) and Oxford knee score was 0.599, 0.690, and 0.871, respectively, suggesting construct validity. Correlation with concurrent measures of physical function from the SF-36 ranged from 0.549 to 0.719 and those of mental function from 0.407 to 0.428. Responsiveness was evident with a standardized response mean of 0.74. The KKS is a reliable and responsive instrument for assessing osteoarthritis. The limited validation studies suggest it is an appropriate evaluation instrument for patients with osteoarthritis and a floor-based lifestyle.