Health institutions and their professional communities develop their own collective tacit knowledge (Collins, 2007, 2010). This tacit knowledge facilitates teamwork within a community or institution, but can create knowledge boundaries (Carlile, 2002, 2004) between professional communities or organizations that would like to work together. These knowledge boundaries can be found in the language or jargon used, representations and interests that can be very different from one organization or community to another (Carlile, 2002). These knowledge boundaries can make it difficult to collaborate between health institutions or professional communities within these institutions (Langley et al. 2019). However, several means are identified in the literature to facilitate the crossing of knowledge boundaries, including boundary objects and boundary spanners (Bechky, 2003; Hargadon, 2003; Obstfeld, 2005; Koskinen, 2005). Boundary objects lead different communities or organizations to exchange together and to explain their tacit knowledge around a common object or project. Boundary spanners know the different communities or organizations involved, and can facilitate exchanges by acting as mediators or translators. We looked at four cases of collaboration that took place during the COVID crisis that involved both boundary objects and boundary spanners that have helped to overcome knowledge boundaries between communities or organizations. It is clear from these cases that these collaborative processes were facilitated by the context. Indeed, the COVID crisis has made it possible to develop conditions that facilitate the emergence of these collaborative processes, in particular thanks to time and spaces for more or less informal exchanges (Detchessahar et al., 2017), and allowing for more collaborative and inclusive management within a pragmatist approach (Elkjaer et al. 2011; Lorino, 2018, 2020).