Factor Analysis of Gait Parameters and Patient-Reported Outcome Measures in Women with Hip Osteoarthritis: A Pilot Study

Background: Gait performance (spatiotemporal and kinetic parameters), physical function (range of motion [ROM] and muscle strength), quality of life (QOL), and other patient-reported outcome measures (PROMs) are interrelated in patients with hip osteoarthritis (HOA). However, the latent structure of these multifaceted factors remains unclear. Therefore, this study aimed to identify the latent factors underlying these multiple indices and investigate their associations. Methods: A total of 33 women with unilateral HOA were included in this study. Gait performance was evaluated using a three-dimensional motion analysis system to extract gait speed, step length, cadence, peak joint power for each phase (hip joint: H1peak–H3peak; ankle joint: A1peak–A2peak), and corresponding joint work (hip joint: H1work–H3work; ankle joint: A1work–A2work). Physical function was assessed by measuring the ROM and muscle strength of the hip and ankle on the affected side. Patient-reported QOL was assessed using the Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ). Factor analysis was performed, with the number of factors fixed at four. Results: The Kaiser–Meyer–Olkin measure was 0.64, indicating “mediocre” sampling adequacy. Factor 1 (comprehensive gait performance) included gait speed, step length, cadence, H2peak, H3peak, A1peak, and hip/ankle strength. Factor 2 (Lower Limb Support in Early Stance and Control of the Stance-to-Swing Transition) included H1peak, A2peak, H1work, A2work, and ankle dorsiflexion ROM. Factor 3 (functional relationship between the hip and ankle joints) included H2work, H3work, hip ROM, and ankle plantarflexion strength. Factor 4 represented the JHEQ subscales: Pain, Movement, and Mental. These four factors explained 73.21% of the total variance. Conclusions: Gait impairment in women with HOA exhibits a multidimensional factor structure encompassing physical function (muscle strength and ROM), biomechanical control of gait (joint power and work), and gait performance (spatiotemporal parameters). Furthermore, gait-related factors may constitute a domain independent of QOL as assessed by PROMs.