The role of thigh muscle and adipose tissue in knee osteoarthritis progression in women: data from the Osteoarthritis Initiative

Objective: To determine whether loss in thigh muscle strength in women concurrent with knee osteoarthritis progression is associated with reductions of muscle anatomical cross-sectional area (ACSA) or specific-strength (i.e., isometric force divided by ACSA), and to explore relationships with local adiposity. Design: Female participants from the Osteoarthritis Initiative with Kellgren-Lawrence grade <= 3, thigh isometric strength measurements, and thigh magnetic resonance images at year-two (Y2) and year-four (Y4) (n = 739, age 62 +/- 9 years; body mass index measurements (BMI) 28.8 +/- 5.9 kg/m(2)) were grouped into: (1) those with vs without symptomatic progression (>= 9 increase in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)-pain [scale: 0-100]); and (2) those with vs without radiographic progression (>= 0.7 mm reduction in minimum joint space width). The change in knee extensor and flexor ACSA and specific-strength, and subcutaneous and intermuscular fat (IMF) ACSAs were compared between progressors and non-progressors using analysis of covariance. Results: Symptomatic progression was associated with a significantly greater loss (p < 0.001) of knee extensor ACSA (- 2.0%, 95% CI -2.5, - 1.5) compared to those without progression (- 0.7%, 95% CI 1.0, - 0.4), and greater loss (p = 0.020) of knee flexor specific-strength (- 7.6%, 95% CI -11.5, - 3.7; vs - 2.4%, 95% CI -4.8, 0.0). Radiographic progression was associated with a significantly greater increase (p = 0.023) in IMF (+1.7%, 95% CI -0.1, +3.6) compared to those without progression (- 0.6%, 95% CI - 1.6, +0.3). Conclusion: The significant reduction in thigh muscle strength concurrent with symptomatic progression in women appears to be associated with loss of extensor muscle ACSA and flexor specific-strength. In contrast, radiographic progression appears to be unrelated to muscle properties, but to be associated with local (intermuscular) adiposity gains. (c) 2018 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.