Kinematic analysis of human movement.

Understanding the kinematics of human movement is of both a basic and an applied value in medicine and biology. Motion measurement can be used to evaluate functional performance of limbs under normal and abnormal conditions. Kinematic knowledge is also essential for proper diagnosis and surgical treatment of joint disease and the design of prosthetic devices to restore function. In general, kinematic analysis of human movement can be categorized into two main areas: 1) Gross movement of the limb segments interconnected by joints, where the relative three-dimensional joint rotation is described by adopting the Eulerian angle system. With proper selection of axes of rotation between two bone segments, the associated finite rotation is sequence independent. This concept is particularly useful, since it matches precisely the clinical definition of joint motion. 2) Detailed analysis of joint articulating surface motion, where generalized three-dimensional, unconstrained rotation and translation are described utilizing the concept of the screw displacement axis. Knowing the surface geometry and soft-tissue constraints, the movement of an articulating joint can be analyzed to provide basic information for lubrication and wear studies. In addition, with appropriate numerical differentiation, velocity and acceleration can be obtained from the displacement information described by the above two methods. Currently available measurement techniques of human movement can be classified into three categories: 1) electrical linkage methods; 2) stereometric methods and biplanar roentgenographic methods; and 3) accelerometric methods. Each system has its unique advantages and limitations in terms of the operational principle, instruments required, data reduction, and type of information produced. Representative analyses of human upper and lower extremity movement will be included as illustrative examples.