The idea of teachers and teacher educators engaging in research is not, in itself, new, but in recent years the propagation of this idea seems to have become really popular. This growing popularity brings the risk that practitioner research will degenerate into an increasingly vague and obscure "container concept". The aim of this article is to pause to allow time to reflect on the concept of practitioner research from a perspective that sees knowledge, knowledge-constitutive interests and knowledge construction as interrelated. (Contains 1 note.)