Orthopaedic pathologies often involve disruption of the mechanical environment of a joint at/below the mm scale. The ability to measure biomechanical kinematics at the sub-mm scale is essential for obtaining valuable insight into pathologies, but small motions of the joints are difficult to quantify. Estimates of skeletal kinematics are commonly made from optical motion capture systems and markers placed on the skin. The error caused by external marker movement is largely avoided with x-ray motion capture. Dynamic radiography uses a series of x-ray images recorded at high-speed and captures in-vivo joint motion. Uncovering the mechanical foundation of orthopaedic pathologies requires accurate and high-speed kinematic measurement of in-vivo 3D, six DOF joint motion. To meet these aims, requirements were established to guide the design, construction, and validation of a high-speed stereo radiography (HSSR) system. The completed system is capable of imaging major joints from the ankle to the cervical spine.