In this paper, we first sketch the joint action theory paradigm from a general viewpoint in sciences of culture. Then we specify this generic description by focusing on the joint action theory in didactics (JATD). We elaborate on three currently developed elements of the theory: the reticence-expression dialectics; the contract-milieu dialectics, through what we call the equilibration process; the didactic semiosis. The empirical part of this paper aims at presenting two empirical studies, which may function as exemplars for JATD, relating to the three aforementioned elements. In the concluding part, we produce a brief synthesis of the main features of our paper, by reframing our empirical analysis. We argue that the didactic contract can be seen as common background in the semiosis process, we show the entanglement between the two kinds of semiosis that we previously delineated, and we conclude by making explicit some features of the comparative approach in didactics.