UCSF

Recent evidence suggests that muscle quality may play an important role in the pathogenesis of hip osteoarthritis (OA). Muscle quality describes the extent of adipose tissue accumulation, or fatty infiltration, within skeletal muscle, as adipose tissue stored within the muscle has the capacity to impair muscle function. The hip abductors are important pelvic stabilizers during gait; therefore, dysfunction of these muscles may impact joint loading and lead to degeneration of cartilage and bone. Despite evidence of increased fatty infiltration in individuals with hip OA, minimal research has evaluated muscle quality in a population with mild-to-moderate OA, and relationships of muscle quality with physical function, joint loading, and cartilage health have been sparsely characterized. In this study, chemical shift-based water-fat separated magnetic resonance (MR) imaging was used to quantitatively evaluate hip abductor muscle quality in a cohort of individuals with and without mild-to-moderate hip OA. Measures of hip abductor muscle quality were related to various disease outcomes including radiographic OA severity, patient-reported disability, functional performance, isometric strength, gait kinematics and kinetics, semi-quantitatively evaluated morphological cartilage degeneration, and biochemical cartilage composition evaluated using quantitative MR imaging. Hip abductor fatty infiltration was found to be significantly associated with worse patient-reported outcomes, functional impairment, cartilage lesions, muscle weakness, and increased frontal plane joint loading. These findings suggest that hip abductor fatty infiltration may contribute to an abnormal mechanical loading environment at the joint, potentially leading to greater cartilage degeneration and disability. These findings are clinically relevant, as muscle quality may be a modifiable risk factor for OA which can be targeted through exercise intervention to improve disease outcomes.