Muscle Power as a Predictor of Knee Osteoarthritis in At-Risk Females - Project Summary The Centers for Disease Control and Prevention estimate that 26% of Americans aged ≥ 18 years will suffer from arthritis by the year 2040. Osteoarthritis (OA) is the most common form of arthritis, with the knee joint being the most commonly affected weight-bearing joint. With no cure on the horizon, it is imperative that preventing knee OA is a health initiative. While risk factors such as age, biological sex, and obesity are well-defined, neuromuscular capabilities are generally neglected in predictive models of incident knee OA. Muscle power (the product of muscle force and muscle shortening velocity) is strongly related to healthy aging in a knee OA population. Maximal muscle power is more strongly correlated to pain and mobility than muscle strength in individuals with knee OA and is significantly associated with a variety of important mobility assessments including walking and sit-to-stand tasks. This ancillary study leverages the patient cohort, data, and resources at baseline and 48-month follow-up of The Osteoarthritis Prevention Study (TOPS) parent randomized clinical trial. The parent trial is nearing the end of year 1 of a 5-year grant period; recruitment began in January 2024, and the first participant was enrolled in March 2024. Maximal knee extensor muscle power measures at baseline will be added to a subsample of participants (N = 159) randomized to the attention control group of the parent grant. The primary aim of this ancillary study is to determine whether the incidence of structural knee OA, defined by MRI Osteoarthritis Knee Score (MOAKS), is predicted by baseline levels of maximal concentric isotonic knee extensor muscle power in a female cohort at- risk for developing knee OA. Secondary aims will determine whether incident structural knee OA is predicted by baseline levels of sit-to-stand task performance and countermovement jump performance, surrogate measures of muscle power that can be administered in a clinical setting. A mechanistic aim will determine whether decrements in knee-joint muscle torque and/or knee-joint angular velocity, factors that determine muscle power, underpin low muscle power and predict incident knee OA in women at high risk for developing knee OA. This ancillary study will contribute novel data regarding a potential mechanistic pathway to incident knee OA, the leading cause of disability in adults. To accomplish our specific aims, we will leverage indices of structural (MRI) OA at baseline and 48-month follow-up from the parent trial and add baseline laboratory (dynamometry) and clinical (sit-to-stand and countermovement jump) measures of muscle power, the latter two that can be easily measured in the clinic. This information could help clinicians identify patients at high risk for this disabling disease by potentially using simple muscle power assessments that can be performed in clinical settings.