Confirmatory Factor Analysis of the Hip Disability and Osteoarthritis Outcome Score (HOOS) and Associated Sub-scales

BACKGROUND: Hip Disability and Osteoarthritis Outcome Score (HOOS), HOOS-Joint Replacement (JR), HOOS Physical Function (PS), and HOOS-12 item scale have been suggested as reliable and valid instruments for assessing hip disability. However, factorial validity, invariance across subgroups, and repeated measures of the scale across different populations have not been well supported in the literature. PURPOSE: The primary study objectives were to: (1) assess model fit and psychometric properties of the original 40-item HOOS scale, (2) assess model fit of the HOOS-JR, (3) assess model fit of the HOOS-PS, and (4) assess model fit of the HOOS-12. A secondary objective was to perform multigroup invariance testing across physical activity level and hip pathology subgroups for models that met recommended fit indices. STUDY DESIGN: Cross-Sectional Study METHODS: Individual confirmatory factor analyses (CFAs) were conducted for the HOOS, HOOS-JR, HOOS-PS, and HOOS-12. Additionally, multigroup invariance testing (i.e., activity level, injury type) was conducted on the HOOS-JR and HOOS-PS. RESULTS: Model fit indices did not meet contemporary recommendations for the HOOS and the HOOS-12. Model fit indices for the HOOS-JR and the HOOS-PS met some, but not all, contemporary recommendations. Invariance criteria was met for the HOOS-JR and HOOS-PS. CONCLUSION: The scale structure of the HOOS and HOOS-12 were not supported; however, preliminary evidence to support the scale structure of the HOOS-JR and HOOS-PS was found. Clinicians and researchers who utilize the scales should do so with caution due to their limitations and untested properties until further research establishes the full psychometric properties of these scales and recommendations for their continued use.