Thigh muscle volume change is associated with longitudinal structural and functional knee osteoarthritis progression - Data from the osteoarthritis initiative.

OBJECTIVE: To investigate the association of change in thigh muscle volume (TMV) with structural knee changes and changes in knee pain and functional limitation over 48 months. DESIGN: Deep learning-based automated segmentations were used to quantify magnetic resonance imaging-derived TMV at baseline and 48 months in 1715 participants from the Osteoarthritis Initiative (mean age 60.0 years; 54.3% women). Participants were categorized by quartile of percentage TMV change over 48 months into muscle loss (Q1: -29.8 to < -7.2%,n = 420), stable muscle (Q2+Q3: -7.2 to <2.4%,n = 864) and muscle gain group (Q4: 2.4-23.7%,n = 431). Structural knee changes were assessed using the Whole-Organ Magnetic Resonance Imaging Score (WORMS), changes in knee pain and functional limitations using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and physical function with the Repeated Chair Stand Test (CST). Associations between TMV changes, WORMS, and functional outcomes were analyzed using multivariable and ordinal regression models. RESULTS: Over 48 months, muscle gain was significantly (p < 0.05) associated with less worsening of bone marrow edema-like lesions (β = -0.29 [95% confidence interval: -0.47, -0.10]), reduced worsening of ligamentous damage (β = -0.12 [-0.22, -0.02]), and less increase in WOMAC pain (β = -0.36 [-0.68, -0.04]) compared to the stable muscle group. Muscle loss was associated with greater tendon damage (β = 0.08 [0.01, 0.15]) and greater declines in CST (β = -0.58 [-1.08, -0.08]). No significant associations were observed between the muscle groups for cartilage and menisci WORMS progression or for physical function (p > 0.05). CONCLUSIONS: Thigh muscle gain was associated with less progression in ligamentous damage and bone marrow edema-like lesions and pain, whereas muscle loss was associated with greater tendon progression and decline in physical performance.