Online communities bring together members of common interest and are recognized as generators of significant knowledge. In healthcare, online communities are a medium for patients to share their stories, gain peer support, and learn more about medical conditions. To succeed, these communities need to sustain their knowledge flows and resolve arising tensions. The current literature suggests that participation dynamics and emergent organizational structure are sufficient to resolve tensions in online communities. Based on increased evidence of the need of formal management to sustain online communities, we propose that emergent structure and roles may not always be sufficient when tensions are prevalent and stakes are high such as in online patient communities. We conduct an inductive field study of Mayo Clinic Connect, a leading online patient community. The findings suggest that formal management and emergent leadership play a complementary role to resolve tensions and sustain knowledge flows. We theorize a virtuous cycle of moderation and socialization that effectively integrates the effort of the community formal management and emergent leaders.