The Knowledge Quartet was originally developed as a framework for reflection on mathematics content knowledge, as evidenced by actual classroom practice. Its scope was later broadened to develop teachers’ SMK and PCK (e.g. Turner, 2008). It was through reflection on their own teaching, guided by the KQ, that participating teachers in this latter study illustrated the utility of the KQ and the development of its conceptions of mathematics teaching and content knowledge, especially PCK, but also SMK.