In this article, I apply the concept of solidarity to collective knowledge practices in healthcare. Generally, solidarity acknowledges that people are dependent on each other in many respects, and it captures those support practices that people engage in out of concern for others in whom they recognise a relevant similarity. Drawing on the rich literature on solidarity in bioethics and beyond, this article specifically discusses the role that epistemic solidarity can play in healthcare. It thus focuses, in particular, on solidarity's relationship with justice and injustice. In this regard, it is argued (1) that justice and solidarity are two equally important and complementary values that should both be considered in healthcare practices and institutions and (2) that solidarity often arises in unjust situations and can be a means to bring about justice. I transfer these 'general' insights about solidarity to knowledge practices in healthcare and link them to the discussion about epistemic injustices in healthcare and how to overcome them. I argue that epistemic solidarity can play an important role in overcoming epistemic injustices as well as-and independently from its contribution to justice-in knowledge production in medicine more generally. To demonstrate how epistemic solidarity can add to our understanding of collective knowledge practices, I discuss two examples: patients sharing their medical data for research purposes and healthcare professionals' engagement with patients to better understand their afflictions.