The general aim of this article is to know about the promotion of knowledge building related to Synthetic Geometry in the initial training of teachers in Mathematics. It is expected to identify, describe and come up with the teaching practices carried out in the first year of the Mathematics Teacher Training career in the National University of Rosario (Argentina). The mathematical knowledge for teaching (MKT) of the Michigan group is taken as a reference. The research has a qualitative approach and is empirical, in its natural context and with descriptive scope. The categories of analysis correspond to the six sub-domains of the MKT. Among the data gathering techniques is the observation of classes and for the data processing the content analysis is applied, starting on the recognition of regularities in registers. Among the main findings is the importance given by the teacher to the students' building of concepts using different strategies. It is concluded that although the teacher makes an approach to the school version of contents, it is not explicitly done to the teachers-to-be.