Safe and effective healthcare requires that new knowledge or skills, once learned, are incorporated into professional practice. However, this process is not always straightforward. Learning takes place in complex contexts, requiring practitioners to overcome various motivational, systemic, emotional, and social barriers to the application of knowledge. This paper explores the mechanisms through which individuals translate knowledge into action to provide insight into why disconnects between knowledge and action can arise. As a critical review, the aim was to draw on key literature from multiple fields to analyse and synthesize existing schools of thought and lay a strong conceptual foundation on which knowledge to action gaps might be considered. We iteratively consulted clinicians and experts in various fields to guide literature searches focused on theoretical perspectives that could inform educational and research efforts around knowledge-to-action gaps. Key theoretical perspectives on motivation address when and how individuals decide to take action. Literatures from cognitive science address how clinicians and learners self-regulate to (sometimes) overcome barriers to action. Sociocultural theories examine the ways in which action might be prevented by social norms that conflict with what the individual knows and believes, potentially also giving rise to counter-normative action. No single perspective will entirely explain how health professionals and learners implement knowledge in practice. As a result, the authors offer multiple lenses through which to view the problem, and then propose how each of these lenses might better guide educational and research efforts to untangle this challenging but important issue.