The Pediatric International Knee Documentation Committee (Pedi-IKDC) Subjective Knee Evaluation Form: Normative Data

Abstract

Background: Children are participating in sports at an increasingly younger age, which has contributed to an increased incidence of knee injuries among this population. Because of increased interest in the application of patient-reported outcome measures in orthopaedic surgery to evaluate treatment results, numerous knee outcome scores, including the International Knee Documentation Committee Subjective Form (IKDC), have been used to evaluate the knee. Although the IKDC has been validated only in adults, it is also being used for children because of a lack of appropriate outcome scores in the pediatric population. To address this concern, a pediatric version of the IKDC (Pedi-IKDC) was developed and evaluated for reliability, validity, and responsiveness. However, normative data for the Pedi-IKDC have not been established. Purpose: We aimed to aid the interpretation of Pedi-IKDC scores by characterizing normative data in children and adolescents and to validate the Pedi-IKDC by examining differences in scores among children who had a history of knee surgery or limited activity compared with those who did not. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We conducted a cross-sectional survey of 2000 children and adolescents aged 10 to 18 years living in the United States, who were recruited by ORC International to obtain equal numbers of participants by sex and by integer age group. Participants were asked to complete the Pedi-IKDC for 1 study-designated “index” knee (right or left) and to provide demographic data and information on their knee surgery history and recent (4-week) activity limitations. Raw Pedi-IKDC total scores were rescaled to a 0 to 100 scale. We used nonparametric Wilcoxon or Kruskal-Wallis tests to compare subgroup scores, and we used the van Elteren test to adjust for age. Unadjusted and adjusted P values were similar, and only unadjusted values are reported. Results: The number of respondents (N = 2000) was uniform with respect to age and sex, with 11% in each age represented (10-18 years). Fifty percent of respondents were female. Forty-nine states plus Washington, DC, were represented. In addition, 68% and 86% of respondents identified themselves as white and non-Hispanic, respectively. Seven percent of respondents (n = 136) respondents reported having prior surgery in 1 or both knees; 4% of these surgeries (n = 79) were in the index knee. The Pedi-IKDC score distribution was skewed left (mean ± SD score, 86.7 ± 16.8; median, 94.6) and 34% of scores reached the ceiling value of 100. Participants who reported prior surgery or limited activity in the index knee had median Pedi-IKDC scores that were approximately 25 points lower than participants without these histories ( P < .0001 for both comparisons). In contrast, although it was statistically significant, the variation by age ( P = .02), race ( P = .02), ethnicity ( P = .01), and level of sports/exercise participation ( P = .04) was much smaller (all ranges of median scores <4.5). There were no significant differences in scores in terms of respondent sex or geographic region. Conclusion: Normative Pedi-IKDC scores were determined in this study. The strong association between Pedi-IKDC scores and prior knee surgery as well as recent activity limitations in the index knee can be used to evaluate clinical outcomes and supports the construct validity of the Pedi-IKDC. There was a large ceiling effect, with 34% of scores at the maximum value of 100. The lack of a sex-based effect and the minor variation with age both simplify the interpretation and use of the Pedi-IKDC. Therefore, Pedi-IKDC score distributions can provide assumptions for use in sample size or power calculations for research.