Reproducibility and responsiveness of a Danish Pedi-IKDC subjective knee form for children with knee disorders

Introduction: The modified International Knee Documentation Committee Subjective Knee Form (Pedi-IKDC) is a widely used patient-reported tool ranging on a scale from 0 to 100. We aimed to translate Pedi-IKDC into Danish and assess its reproducibility and responsiveness in children with knee disorders. Methods: The translation complied with the international guidelines. Reproducibility was assessed in 53 children (15 years) responding Pedi-IKDC at baseline and after 3–14 days. For analysis of responsiveness, 94 children (15 years) responded Pedi-IKDC again after 3 months. Results Test–retest reliability was excellent. Intraclass correlation coefficient was 0.9, standard error of Measurement was 4.1 points, and smallest detectable change (SDC) was 11.3 points. Evaluating responsiveness as a large effect was found in children reporting improvement with children reporting deterioration. The change score was correlated to the external anchor Global Scale consisting of 15 answers from −7 “A very great deal worse” to +7 “A very great deal better,” with a Spearmen’s rho of 0.45 (P > 0.001). The minimal clinically important changes was 12.0. Conclusion In conclusion, excellent test–retest reproducibility was found at group level, but at individual level the SDC was high. The Pedi-IKDC showed adequate responsiveness and is suitable for assessing improvement or deterioration in children with knee disorders.