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. 2019 May/Jun;11(3):242-246.
doi: 10.1177/1941738118812454. Epub 2018 Nov 16.

KOOS-JR Demonstrates Psychometric Limitations in Measuring Knee Health in Individuals After ACL Reconstruction

Jennifer L Hunnicutt  1 , Brittany N Hand  2 , Chris M Gregory  3   4 , Harris S Slone  5 , Michelle M McLeod  6 , Brian Pietrosimone  7 , Christopher Kuenze  8 , Craig A Velozo  4   9
Affiliations

KOOS-JR Demonstrates Psychometric Limitations in Measuring Knee Health in Individuals After ACL Reconstruction

Jennifer L Hunnicutt et al. Sports Health. 2019 May/Jun.

Abstract

Background: Measurement properties of the short form of the Knee injury and Osteoarthritis Outcome Score (KOOS-JR) are not established in individuals after anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to determine the extent to which the KOOS-JR measures the construct of knee health in individuals post-ACLR using Rasch analysis.

Hypothesis: The KOOS-JR will fit the Rasch model, but significant ceiling effects will be present.

Study design: Cross-sectional study.

Level of evidence: Level 3.

Methods: Rasch analysis of the KOOS-JR from 166 individuals 10 months post-ACLR was conducted. Unidimensionality, a key criterion of the Rasch model, was evaluated using confirmatory factor analysis. Model fit of the rating scale, items, and persons were evaluated. Mean square fit statistics ≥1.6 and standardized z-scores ≥2.0 were indicative of person or item misfit. Additionally, reliability indicators including person reliability and separation indices were examined.

Results: The KOOS-JR fit the criteria of unidimensionality. All items demonstrated model fit; however, ceiling effects were noted (n = 36; 22%). Person reliability was low (0.47). Calculation of person strata revealed that the KOOS-JR did not separate participants into more than 1 stratum. The mean person measure was 3.56 logits higher than the mean item measure, indicating that this sample is skewed toward increased knee health.

Conclusion: Although the KOOS-JR represented a unidimensional construct with items and persons fitting the Rasch model, several limitations were noted: ceiling effects, low person reliability, and poor person differentiation. Ceiling effects indicate that many individuals in this sample experienced better knee health than the KOOS-JR items were able to measure.

Clinical relevance: Evaluating the measurement properties of the KOOS-JR is necessary to determine its clinical value in sports medicine. In later stages after ACLR recovery, administration of the KOOS-JR may not be adequate.

Keywords: KOOS-JR; Rasch; anterior cruciate ligament reconstruction; patient-reported outcomes; rehabilitation.

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Conflict of interest statement

The authors report no potential conflicts of interest in the development and publication of this article. This project was supported by the South Carolina Clinical & Translational Research (SCTR) Institute, with an academic home at the Medical University of South Carolina, through NIH Grant Numbers TL1 TR001451 and UL1 TR001450.

Figures

Figure 1.
Figure 1.
Person-item map. The right side of the map represents the 7 items of the KOOS-JR, anchored at 0. The left side of the map represents persons. Persons are a mean of 3.56 logits higher than the mean item measure, which is anchored at 0. Each “#” is 3 persons; each “.” is 1 to 2 persons. KOOS-JR, short form of the Knee injury and Osteoarthritis Outcome Score.
See this image and copyright information in PMC

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