Changes in limb or joint anatomy, e.g. due to injury or surgery, may lead to functional impairment. Accurate measurement of skeletal kinematics provides the key to understanding the role of joint instabilities on the onset and progression of degenerative diseases. The aim of the project is to measure knee joint motion in vivo and to identify and characterize joint laxity. In order to assess relative motion of knee joint structures, dynamic medical imaging techniques are used. Possible options are fluoroscopy, dynamic CT, and MRI. The most practical approach is fluoroscopic imaging due to the possibility of imaging knee joint structures during physical exercises at affordable costs. One of the challenges addressed in this project is the reconstruction of anatomical structures from 2D images. Via a combination of MRI and fluoroscopy data and based on the developed 3D reconstruction techniques within the project '3D From Xray' we will assess and improve skin marker-based methods for assessing skeletal dynamics and joint centers.