Reliability, Validity, and Responsiveness of a Modified International Knee Documentation Committee Subjective Knee Form (Pedi-IKDC) in Children With Knee Disorders

Abstract

Background: The International Knee Documentation Committee (IKDC) Subjective Knee Form is a knee-specific measure of symptoms, function, and sports activity. A modified IKDC Subjective Knee Form (pedi-IKDC) has been developed for use in children and adolescents. The purpose of this study was to determine the psychometric characteristics of the pedi-IKDC in children and adolescents with knee disorders. Hypothesis: The pedi-IKDC is a reliable, valid, and responsive patient-administered outcome instrument in the pediatric population with knee disorders. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Test-retest reliability, content validity, criterion validity, construct validity, and responsiveness to change were determined for the pedi-IKDC in patients aged 10 to 18 years with a variety of knee disorders. Test-retest reliability was measured in a group of 72 patients with a stable knee disorder. Validity was measured in a group of 589 patients with the Child Health Questionnaire to determine criterion validity. Responsiveness was measured in a group of 98 patients undergoing a variety of knee surgical procedures. Results: The overall pedi-IKDC had acceptable test-retest reliability (intraclass correlation coefficient, .91) and excellent internal consistency (Cronbach alpha, .91). The form also demonstrated acceptable floor (0%) and ceiling (6%) effects. There was acceptable criterion validity with significant ( P < .01) correlation between the overall pedi-IKDC and 9 relevant domains of the Child Health Questionnaire. Construct validity was acceptable, with all 11 hypotheses demonstrating significance ( P < .0001). Responsiveness to change was acceptable (effect size, 1.39; standardized response mean, 1.35). Conclusion: The pedi-IKDC demonstrated overall acceptable psychometric performance for outcome assessment of children and adolescents with various disorders of the knee.