Reliability, validity, and responsiveness of the IKDC score for meniscus injuries of the knee

Purpose: The purpose of this study was to determine the psychometric properties of the International Knee Documentation Committee (IKDC) score for meniscus injuries of the knee. Methods: Test-retest reliability, content validity, construct validity, and responsiveness to change were determined for the IKDC score. Knees were excluded if they had ligament pathology or a chondral defect greater than Outerbridge grade 2. All patients had meniscus pathology requiring treatment. The study comprised 4 subsets of patients. Group A consisted of 31 patients who completed an IKDC form at least 2 years after surgery for meniscus pathology and were then retested within 4 weeks of the primary questionnaire. Group B contained 264 patients with preoperative IKDC scores that were used for construct and content validity. Group C contained 50 patients who had a preoperative IKDC score and completed a short form 12 survey. Group D contained 100 patients with preoperative and postoperative IKDC scores used to measure responsiveness. Results: The overall IKDC score showed acceptable test-retest reliability with an interclass correlation of 0.95. There were acceptable floor and ceiling effects. All constructs tested showed significant differences. These included lower IKDC score with the following: lower activity level, difficulty with activities of daily living, difficulty with sports, abnormal knee function, and complex/degenerative meniscus tears. Responsiveness to change showed a large effect size (2.11) and a large response mean (1.5) for the overall score. The SE of the measurement was 3.19, and the minimum detectable change was 8.8 points. Conclusions: The overall IKDC score showed overall acceptable psychometric performance for outcome measures of meniscus injuries of the knee. Level of Evidence: Level 111, testing of previously developed diagnostic criteria in nonconsecutive patients.