A knee testing rig is a biomechanical testing device specifically designed for investigating the kinematics and kinetics of cadaveric human knee-joint specimens during knee-flex stance simulations. Current in-vivo measurements of patients can provide assessments of displacement and rotation but do not permit quantification of internal forces and movement of internal structures. More importantly, the detailed study of the effects of surgical reconstruction methodologies, implant designs and knee pathologies on lower extremity mechanical is only possible using knee testing rigs in the laboratory. We proposed the design of a knee rig with aims to measure these parameters under a full body weight knee simulation. The knee rig may potentially be used to investigate the effect of ligament injury, post-surgical ligament reconstruction, and evaluating implant designs in terms of its resulting knee kinematics and load distribution. A CAD model of the rig was designed and evaluated using SolidWorks and then machined. The constructed rig consists of ‘hip’ and ‘ankle’ assemblies, which combine to allow a natural six degrees of freedom of movement. These include three rotations: flexion/extension, abduction/adduction, internal/external tibia rotation and three translations: anterior/posterior, medial/lateral, proximal/distal. Knee simulation is performed by pulling the quadriceps tendon of a cadaveric knee specimen to produce a realistic muscle action. A 6-axis load cell (AMTI MC3A–6-1000) is used to collect force/moment data. A motion capture system is used to measure the resulting knee kinematics during flexion.