Determination of the Mechanical Function of Human Knee Joints using Robotics

A robotic system has been developed to determine the mechanical function of human knee joints in six degrees of freedom. The system consisted of a six-axis articulated manipulator, a universal force-moment sensor, custom clamps for joint fixation, and a computer for manipulator control and data acqusition. Using the position control and force control, the position/orientation of and force/moment applied to the human knee joint can be measured and controlled with respect to a knee joint coordinate system originally developed by Grood and Suntay. Moreover, it was possible to reproduce the three-dimensional path of knee motion using the position control. To verify this system, two cadaveric human knee specimens were used to determine the effects of anterior-posterior force and varus-valgus moment on the three-dimensional knee motion. The data agreed well with clinical observations, as well as previously determined biomechanical data, such as internal rotation and external rotation with anterior and posterior forces to the knee. It was found that the system is especially applicable to "sequential section" which is one of methods for the study of joint biomechanics.