Online health communities offer unprecedented opportunities of empowering patients to take care of their own health and reducing the pressure of chronic diseases on the health service. Given the importance of knowledge for the empowerment of patients, the objective of this study is to understand the impact of knowledge sharing in online health communities on various aspects of health self-management. We develop a model to investigate 1) the factors that influence the level of community engagement in online communities and 2) the impact of engagement in online communities on members’ cognitive, behavioral, and emotional experiences of health self-management. We will empirically test our model through an online survey with the users of Diabetes.co.uk's forum. The study aims to provide a holistic perspective on the impact of a properly managed online health community on patients’ wellbeing.