Project Summary/Abstract Osteoarthritis (OA) is a leading cause of pain and disability among older adults. Physical activity (PA) is critical for managing OA and improves many outcomes including physical function and disability risk. Unfortunately the vast majority of individuals with OA are physically inactive, with only 10% meeting PA recommendations. There is a critical need to improve PA levels in this vulnerable patient group. The proposed project will develop and test an OA primary care Physical activity Care Pathway (OA-PCP), a scalable intervention that includes: 1) a practical process for physical inactivity screening in primary care, 2) a brief, tailored PA counseling intervention via telephone, 3) connection of patients with community programs and other resources to support PA, and 4) follow-up with patients to deliver additional appropriate counseling and referrals to PA resources. The OA-PCP is designed with implementation and sustainability in mind, particularly modeled for delivery in the context of billable Chronic Care Management services. Aim 1 of the project will involve focus groups and structured interviews with patients who have OA, primary care providers, and community / clinical PA program leaders to develop the OA-PCP. Aim 2 will assess the feasibility and acceptability of the OA-PCP among n=60 patients with hip and knee OA in two primary care clinics. All patients in the trial will participate in the OA-PCP and will complete assessments at baseline and 4-month follow-up. Feasibility metrics will include rates of recruitment, intervention engagement and retention; acceptability will be assessed from both patients and health care providers. Aim 3 will involve a randomized pilot trial assessing the efficacy of the refined OA-PCP (from Aims 1 and 2) among n=240 patients with knee and hip OA in six diverse primary care clinics. Patients in the study will be randomized to the OA-PCP or an attention control group and will complete assessments at baseline, 6-months and 12-months. The primary outcome will be objectively assessed physical activity, measured via accelerometry. Linear mixed models will compare outcomes between the OA-PCP and attention control groups. The OA-PCP will be designed for widespread implementation and therefore has strong potential to improve PA among individuals with OA at a population health level. This series of exploratory / developmental projects will set the stage for and inform the development of a large, multisite implementation- focused study of the OA-PCP.