Many clinicians are moving away from the traditional expert role towards a more collaborative approach to clinical decision making. Collaboration with patients has implications for the power distribution between clinician and patient, how health is defined, and what counts as evidence in the decision-making process. A critical social science perspective provides the philosophical and theoretical underpinnings for collaborative clinical decision making. Key issues of critical social science are critical self-reflection, questioning taken-for-granted practice, and transforming current practice. The way that clinicians define their role in clinical decision making reflects their beliefs and values about health, power and practice knowledge. Clinicians who adopt a collaborative clinical decision-making approach reject the objective scientific view of evidence-based practice, and embrace cultural and political influences on what counts as evidence. The purpose of collaboration is to increase understanding between the clinician and the patient. A distinction is made in this debate between manipulating and emancipating patients. Including patients in the decision-making process promises to result in more realistic and appropriate treatments, reduced patient concerns and complaints and better, sustainable health outcomes, and increased patient and clinician satisfaction. In this article we re-think practice knowledge and the notion of clinician'patient relationships.