Co-creation is an emerging form of collaborative governance enabling multi-source knowledge integration to tackle societal challenges. Yet, conceptualisations of the role of knowledge in co-creation remain scarce. In search of lessons on this matter, this article conducts a literature review, producing the outline of a heuristic that captures how the alignment of knowledge conditions explains the co-creation of social innovations. The proposed heuristic challenges deterministic accounts of knowledge in co-creation as a mere input/resource by shedding light on its cognitive, performative, relational, and contextual dimensions. This approach suggests further exploring network structures of knowledge circulation, social innovation pathways, and knowledge practices in co-creation processes.