Climate change, armed conflicts, widening inequities, pandemics, and large-scale displacement represent deeply entangled challenges for contemporary public health. While transdisciplinarity is increasingly invoked as a response to this complexity, it is often reduced to collaboration across academic disciplines, leaving experiential knowledge at the margins.

In this paper, I argue that experiential knowledge is not a supplementary input but a constitutive form of transdisciplinary expertise. Drawing on traditions in social medicine and critical social theory, including the work of Michel Foucault, Kimberlé Crenshaw, Patricia Hill Collins, and Paul Farmer, I examine how power structures shape what counts as legitimate knowledge in public health. I further engage with Emily Yates-Doerr’s critique of the social determinants of health framework to demonstrate how dominant epistemological approaches can produce forms of “problem closure” that render certain structural issues analytically marginal.

Using examples from the CANCERLESS project, I illustrate how participatory co-design and engagement with lived experience can reconfigure both problem definitions and intervention strategies. I argue that integrating experiential knowledge is not merely a question of participation but an epistemic necessity. Without it, public health risks producing knowledge that is methodologically rigorous yet disconnected from the realities it seeks to address.