Abstract
OBJECTIVES: To aid in the interpretation of Pedi-IKDC scores by characterizing normative data in children and adolescents. Also, to validate the Pedi IKDC by examining differences in Pedi IKDC scores between patients with knee ailments compared to patients without a history of knee problems. METHODS: Cross sectional survey of 2000 children and adolescents aged 10-18 years living in the United States, recruited by ORC International to obtain equal numbers by sex and by integer age group. In addition to completing the Pedi-IKDC for one study designated “index” knee (right or left), subjects were asked demographic questions and for information on history of knee surgery and recent (four weeks) activity limitations. Raw Pedi-IKDC total scores were re scaled to a 0-100 scale. Non-parametric Wilcoxon or Kruskal-Wallis tests were used to compare subgroup scores and the van Elteren test was used to adjust for age. Unadjusted and adjusted p values were similar and only unadjusted values are reported. RESULTS: Numbers of respondents are uniform with respect to age and sex, with 11% in each age group (10-18) and 50% female. 68% identified themselves as white, and 86% as non-Hispanic. 49 states and DC are represented. 136 (7%) reported prior surgery in one or both knees; 79(4%) in the index knee. The Pedi IKDC score distribution is skewed left with mean score (±SD) of 86.7(±16.8), median 94.6 and 34% reaching the ceiling value of 100. Subjects reporting prior surgery or limited activity in the index knee had median Pedi IKDC scores about 25 points lower than those without these histories (p<0.0001 for both comparisons). In contrast, although statistically significant, the variation by age (p=0.02), race (p=0.02), ethnicity (p=0.01), and level of sports/exercise participation (p=0.04) was much smaller (all ranges of median scores <4.5). There were no significant differences by sex or geographic region. CONCLUSION: There is only minor variation in Pedi IKDC scores across demographic factors. The strong association between Pedi IKDC score and prior knee surgery and also with recent limitation of activity in the index knee supports the construct validity of the Pedi-IKDC. Using a large, broadly representative sample, this study supports the use of the Pedi-IKDC as a knee specific outcome instrument for pediatric patients aged 10-18 and provides normative values to aid the interpretation of scores in this age range.