In this paper, we present a new model to analyse therapeutic games. The goal of the model is to describe and analyse the relations between the three aspects of a therapeutic game: the player, the game, and the therapy. The model is intended to game designers. It is a tool to improve the communication between health experts and game designers, and to evaluate the game design coherency of therapeutic games. It also helps to analyse existing games to discover relevant features. The model is built with respect to existing serious game definitions and taxonomies, medical definitions, motivation theory, and game theory. We describe how the model was used to design le village aux oiseaux, a therapeutic game which goal is to train people with attention disabilities. In the last section, we present the results of analysis done with our model and discuss the model limits.