Apparatus and method are disclosed for assessing rotational bone kinematics. Instantaneous center of rotation (ICR) of a bone segment is derived from a digitalized image of a bone and it is compared with the normal distribution of an ICR to determine rotational bone kinematics. The apparatus and method may be used to assess kinematic status of a normal bone and pathological bone. They also may be used to design an improved artificial disc to provide an appropriate kinesis.