Quality of teaching relies on the degree of teachers` understanding of the content they teach. This understanding influences decisions teachers make when they plan, execute and adapt their instruction. Developing teaching quality requires a specific focus on teaching practices. These are issues of content knowledge and Pedagogical Content Knowledge (PCK) in physical education. Substantial progress has been made in the understanding of content knowledge and pedagogical content knowledge, and in the methodologies by which these bases can be empirically measured. This presentation will introduce the conceptual and analytical evolution of pedagogical content knowledge in physical education, which has been known and discussed in the past three decades as an abstract heuristic construct. Next, the novel theoretical discriminations, Common Content Knowledge (CCK) and Specialized Content Knowledge (SCK) will be presented and explained. Finally, research findings will be presented to illustrate the empirical knowledge that has emerged in the empirical investigation of CCK and SCK in international countries.