Pedagogical content knowledge (PCK) is a frequently used concept in the educational community. Its usage is so widespread it appears to function as a "lingua franca" across different subject areas and among researchers within a subject area. Critiques of PCK have suggested it may function at best as a heuristic and at worst as a masquerade; because there has been little consensus on its conceptualization and in many studies there is no operational definition of PCK provided. Recent studies, however, have moved both the conceptualization and measurement of PCK forward in ways that allow the concept to be operationalized. In this article we examine how PCK has evolved since Shulman's (1986) initial conceptualization, and discuss how the concept has been used in physical education. We describe and examine five recurring research findings for PCK in physical education. These are that PCK can be described on continuums of maturity and effectiveness; is learned, is specific to content and context; and is strongly related to both content knowledge and knowledge of students.