A system which extracts motion data from a video image of an infant, and determines synchronism, symmetry, and/or coordination among the limbs. The system uses the synchronism, symmetry, and/or coordination results to determine whether the infant has a disease and/or what disease it may be. The system uses as an index for coordination one or more of: a movement start/stop order and acceleration of the markers; the trajectory, speed, or acceleration of a midpoint of a line connecting markers attached to various combinations of the arms and legs; and the trajectory, speed, and acceleration of a gravity center of a plane connecting three markers attached to various limbs.