Validity and Internal Consistency of the International Knee Documentation Committee Subjective Knee Evaluation Form in Children and Adolescents

Background: The International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form (IKDC Knee Form) is a valid, reliable, and responsive measure of knee-related symptoms, function, and sports activities in adults. Despite the incidence of knee injuries in younger individuals, the measurement characteristics of the IKDC Knee Form have not been established. Hypothesis/Purpose: The purpose of this study was to investigate the validity and internal consistency of the IKDC Knee Form in pediatric, adolescent, and young adult patients with a variety of knee conditions. The authors hypothesized that the IKDC Knee Form would be a valid and consistent measure of knee function in these age groups. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: The IKDC Knee Form and Pediatric Quality of Life Inventory 4.0 Generic Core Scales (PedsQL) physical functioning component were administered to 673 individuals between 6 and 18 years of age. The internal consistency and validity of the IKDC Knee Form were determined for the entire cohort and for age group cohorts (pediatric, 6-12 years; adolescent, 13-15 years; young adult, 16-18 years) using the PedsQL physical functioning component for comparison. Results: The results were similar across all age groups. In the original format, internal consistency was high and factor analysis showed a single, dominant component underlying the item responses for each age group. Items 2, 3, and 6 may contribute to measurement error in young individuals. Correlation between the IKDC Knee Form and PedsQL physical functioning component score was moderately high for the entire cohort (r = .83) and for all age groups (pediatric, r = .84; adolescent, r = .84; young adult, r = .79). Conclusion: In its current form, the IKDC Knee Form is a valid and consistent knee-specific measure of symptoms, function, and sports activity in individuals between the ages of 6 and 18 years with a variety of knee problems. Further work is needed to establish the reliability and responsiveness of the IKDC Knee Form for this age group.