The Osteoarthritis Prevention Study

The goal of this study is to establish the efficacy of an intervention of dietary weight loss, exercise, and weight-loss maintenance for knee Osteoarthritis (OA) prevention in adult females aged ≥ 50 years with obesity and no or infrequent knee pain. The primary aim is to compare the effects of a dietary weight loss, exercise, and weight-loss maintenance to an attention control group in preventing the development of structural Magnetic Resonance Imaging (MRI) knee OA. Secondary aims will determine the intervention effects on pain, mobility, health-related quality of life, knee joint compressive forces, inflammatory measures, weight loss, exercise self-efficacy, and cost-effectiveness of this intervention.

Inclusion Criteria: * Female * BMI ≥ 30 kg/m2 * An eligible knee will have no OA by xray and MRI * No or infrequent knee pain (\< 15 days/month) in the same knee Exclusion Criteria: * symptomatic or severe coronary artery disease * unable to walk without a device * blindness * type 1 diabetes * active treatment for cancer * during the past 12 months knee fracture, anterior cruciate ligament (ACL), medial collateral ligament (MCL), or meniscus injury with or without surgical repair * knee injection during the past 6 months * bilateral knee OA by x-ray Kellgren-Lawrence (KL) ≥ 2 * bilateral knee OA by MRI * bilateral symptomatic knee OA (frequent bilateral knee pain \> 15 days per month) * BMI\< 30.0 kg/m2 * male sex * claustrophobia * contraindication to MRI including body weight \> 300 lbs or knee coil does not fit * unwillingness or inability to change eating and physical activity habits due to environment * cannot speak and read English * planning to leave area \> 2 months during the 48-month intervention period