Purpose: Using three separate models that included total body mass, total lean and total fat mass, and abdominal and thigh fat as independent measures, we determined their association with knee joint loads in older overweight and obese adults with knee osteoarthritis (OA).
Methods: Fat depots were quantified using computed tomography, and total lean and fat mass were determined with dual energy x-ray absorptiometry in 176 adults (age, 66.3 yr; body mass index, 33.5 kg·m−2) with radiographic knee OA. Knee moments and joint bone-on-bone forces were calculated using gait analysis and musculoskeletal modeling.
Results: Higher total body mass was significantly associated (P ≤ 0.0001) with greater knee compressive and shear forces, compressive and shear impulses (P < 0.0001), patellofemoral forces (P < 0.006), and knee extensor moments (P = 0.003). Regression analysis with total lean and total fat mass as independent variables revealed significant positive associations of total fat mass with knee compressive (P = 0.0001), shear (P < 0.001), and patellofemoral forces (P = 0.01) and knee extension moment (P = 0.008). Gastrocnemius and quadriceps forces were positively associated with total fat mass. Total lean mass was associated with knee compressive force (P = 0.002). A regression model that included total thigh and total abdominal fat found that both were significantly associated with knee compressive and shear forces (P ≤ 0.04). Thigh fat was associated with knee abduction (P = 0.03) and knee extension moment (P = 0.02).
Conclusions: Thigh fat, consisting predominately of subcutaneous fat, had similar significant associations with knee joint forces as abdominal fat despite its much smaller volume and could be an important therapeutic target for people with knee OA.
1Department of Health and Exercise Science, Wake Forest University, Winston-Salem, NC; 2Department of Biostatistical Sciences, Wake Forest School of Medicine, Wake Forest University, Winston-Salem, NC; 3Section on Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Wake Forest University, Winston-Salem, NC; 4Department of Exercise and Sport Science, East Carolina University, Greenville, NC; 5Department of Radiology, Wake Forest School of Medicine, Wake Forest University, Winston-Salem, NC; 6Department of Rheumatology, Royal North Shore Hospital and Kolling Institute, University of Sydney, Sydney, AUSTRALIA; 7Section on Molecular Medicine, Wake Forest School of Medicine, Wake Forest University, Winston-Salem, NC; and 8Department of Rheumatology and Immunology, Wake Forest School of Medicine, Wake Forest University, Winston-Salem, NC
Address for correspondence: Stephen P. Messier, Ph.D., J. B. Snow Biomechanics Laboratory, Department of Health and Exercise Science, Wake Forest University, Winston-Salem, NC 27109; E-mail: firstname.lastname@example.org.
Submitted for publication September 2013.
Accepted for publication January 2014.