A. Project Summary or Abstract: Mobility disability impacts approximately 30% of individuals aged 60-69, 40% of individuals aged 70-79, and 55% of individuals age 80 or older. Emerging cross-sectional evidence suggests that self-reported musculoskeletal pain may be one of the major drivers of age-related mobility decline. Despite this evidence, significant knowledge gaps remain because the relationships among chronic musculoskeletal pain, aging, mobility, psychosocial function, and the brain have not been studied longitudinally in the same older individuals. Our prospective study design will provide novel information on the role of pain-related brain changes as predictive factors of age-related mobility decline. The proposed work will allow us to determine whether pain as well as brain structure and function predict mobility decline longitudinally (Aim 1) and whether brain measures mediate the pain-mobility association prospectively (Aim 2). The proposed work integrates multiple fields of study within a biopsychosocial approach to study pain and mobility in the older population.