Therapeutic game adaptation is an important feature allowing the personalization of the patient's motor re-learning while maintaining her/his engagement and motivation. This article presents a dynamic difficulty adaptation technique dedicated to a family of therapeutic games for upper-limb post-stroke rehabilitation. The proposed technique is based on players' profile and prior clinical assessment of their physical capabilities. It provides a generic real-time adaptation module to dynamically adapt the game experience to each patient according to her/his observed performances and capabilities. An initial prototype and a pre-pilot experiment on healthy people are presented to demonstrate how this technique has been preliminary implemented and could be tested for post-stroke therapeutic games.