Moving objects are present in most scenes of our life. However they can be very problematic for classical SLAM algorithms that assume the scene to be rigid. This assumption limits the applicability of those algorithms as they are unable to accurately estimate the camera pose and world structure in many scenarios. Some SLAM systems have been proposed to detect and mask out dynamic objects, making the static scene assumption valid. However this information can allow the system to track objects within the scene, while tracking the camera, which can be crucial for some applications. In this paper we present TwistSLAM a semantic, dynamic, stereo SLAM system that can track dynamic objects in the scene. Our algorithm creates clusters of points according to their semantic class. It uses the static parts of the environment to robustly localize the camera and tracks the remaining objects. We propose a new formulation for the tracking and the bundle adjustment to take in account the characteristics of mechanical joints between clusters to constrain and improve their pose estimation. We evaluate our approach on several sequences from a public dataset and show that we improve camera and object tracking compared to state of the art.