The focus of this proposal is to conduct a proof of concept RCT to establish the efficacy of a behavioral economics-based intervention that would facilitate engagement in physical activity and improve adherence to PA guidelines in the growing population of TKR recipients. We address the innovative hypothesis that the period following TKR presents a window of opportunity to fundamentally change attitudes and beliefs regarding PA, and that tangible economic incentives will effectively induce behavior change and facilitate adherence to PA guidelines.