Development of a brief core set for knee dysfunction based on the International Classification of Functioning, Disability and Health: assessing construct validity and measurement potential

Abstract

Abstract Background The comprehensive core set for knee dysfunction was developed to classify the functioning of people with any knee dysfunction. To be used as a clinical instrument to measure the functioning of people with knee dysfunction, the construct validity of the core set still needs to be assessed. The purpose of this study was to analyze the construct validity of the comprehensive core set for knee dysfunction as an instrument to measure functioning. Methods A cross-sectional study with 200 participants with knee dysfunction with or without clinical diagnosis of knee pathology, with or without complaint of pain, with or without instability, and/or with or without knee movement restriction of any type. Participants were assessed using the comprehensive core set for knee dysfunction with 25 categories, the subjective form from the International Knee Documentation Committee scale, and measures of self-perceived general health and functioning. The construct validity of the core set was assessed by Rasch analysis, and the external construct validity was assessed by correlation between the score of the brief core set for knee dysfunction with the subjective form from the International Knee Documentation Committee scale, and scores of self-perception of health and functioning. Results Twelve categories were consistent with a unidimensional construct, with no difference in the response pattern for age, sex, educational level, and time of complaint. These categories were included in the brief core set for knee dysfunction. The mean score of the brief core set was 37 ± 21 points, a value classified as moderate impairment regarding functioning. Correlations with the subjective form from the International Knee Documentation Committee scale and scores of self-perception were adequate (p < 0.01; r > 0.5). Conclusion The brief core set for knee dysfunction, a set with 12 categories, can be used as a clinical instrument to measure and score the functioning of people with knee dysfunction, aged between 18 and 89 years, with adequate construct validity.