Height of centre of body mass during osteoarthritic gait

Early attempts to locate the position of the centre of mass of the body during walking involved the use of cinematography, followed by kinetic analysis of the forces and couples acting about three axes at the ground and centre of mass. These methods, requiring data on the individual body segments, are too lengthy and complex for routine clinical use. A method is described which estimates both the trajectory and the mean height of the centre of mass, using only dynamic data from a single walk across one pair of force plates. Relating a possible trajectory height to the measured force vectors gives a profile for the horizontal velocity. The correct height is determined by seeking the smooth profile corresponding to the known horizontal velocity obtained by integration. Results are presented for 42 osteoarthritic patients undergoing total hip replacement operations.