INTRODUCTION Characterisation of in vivo thumb kinematics allows precise biomechanical analysis of healthy and pathological joint movement. When movement characteristics and musculoskeletal structure are combined, more insight can be gained on the relation between anatomy and function in native and diseased joints. However, due to the complex 3D arrangement of the small carpal bones with multi-planar range of motion and skin movement artefacts, it is difficult to determine the in vivo movements using standard 3D motion capture techniques. Thumb kinematics have been investigated using various methods, e.g. static CT scans, fluoroscopy, high-speed video, opto-electricand electromagnetic-based systems. However, none of these methods allows direct evaluation of 3D bone movement. The most important drawback of the various motion tracking systems are the skin motion artefacts, in particular for the carpal bones. Fluoroscopic techniques are difficult due to the complex, superimposed arrangement of the small carpal bones that are difficult to individualize on 2D projections. To overcome these problems, and to acquire an accurate characterization of the 3D kinematics of bones involved in thumb opposition, a dynamic CT motion capture protocol was developed and tested.