Reliability and Validity of the IKDC, KOOS, and WOMAC for Patients With Meniscal Injuries

Abstract

Background: Several patient-reported outcome measurements are used to measure functional outcome after treatment of meniscal injuries. However, for comparison of study results, there is a need for a uniform and standardized approach of measuring functional outcome. Selection of the instrument should be based on the quality of its measurement properties, and only the best instrument can be justified to be used.

Purpose: This study aimed to determine and compare the measurement properties of the Dutch-language versions of the International Knee Documentation Committee (IKDC) Subjective Knee Form, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Western Ontario and McMaster Universities Arthritis Index (WOMAC) in a homogeneous group of patients with meniscal tears.

Study design: Cohort study (design); Level of evidence, 2.

Methods: Patients on the waiting list for meniscal surgery and patients between 6 weeks and 6 months after meniscal surgery were included (n = 75). Patients were excluded if they received an arthroplasty or had surgery on the anterior cruciate ligament. Internal consistency (Cronbach alpha), test-retest reliability (intraclass correlation coefficient [ICC]), measurement error (SEM), smallest detectable difference (SDD), content validity, construct validity (factor analysis and hypothesis testing), and floor and ceiling effects were determined.

Results: Results for the IKDC, KOOS dimensions, and WOMAC dimensions, respectively, were as follows: Cronbach alpha = .90, .72-.95, and .84-.95; ICC = 0.93, 0.84-0.89, and 0.77-0.89; SEM = 5.3, 7.0-12.6, and 7.3-12.2; SDD = 14.6, 19.4-35.0, and 20.2-33.9; hypotheses testing confirmation = 100%, 86%, and 85%. Floor effects within the SDD from the minimum score were found for the KOOS Sports/Recreation and Quality of Life dimensions. Ceiling effects within the SDD from the maximum score were found for the KOOS Activities of Daily Living and for all WOMAC dimensions.

Conclusion: The IKDC showed the best performance on all measurement properties, implying that the IKDC, rather than the KOOS or WOMAC, should be used to assess functional outcome in patients with meniscal tears.

Keywords: IKDC; KOOS; WOMAC—measurement properties; knee—meniscus; patient-reported outcome measurement.