EFFECT OF SKIN MOVEMENT ON THE ANALYSIS OF SKELETAL KNEE-JOINT MOTIONDURING RUNNING

It is not known how well skin markers represent the skeletal knee join t motion during running. Hence, the purpose of this investigation was to compare the skin marker derived tibiofemoral motion with the skelet al tibiofemoral motion during running. In addition to skin markers att ached to the shank and thigh, triads of reflective markers were attach ed to bone pins inserted into the tibia and femur. Three-dimensional k inematics of the stance phase of five running trials were recorded for three subjects using high-speed cine cameras (200 Hz). The knee motio n was expressed in terms of Cardan angles calculated from both the ext ernal and skeletal markers. Good agreement was present between the ski n and bone marker based knee flexion/extension. For abduction/adductio n and internal/external knee rotation, the difference between skeletal and external motion was large compared to the amplitude of these moti ons. Average errors relative to the range of motion during running sta nce were 21% for flexion/extension, 63% for internal/external rotation , and 70% for abduction/adduction. The errors were highly subject depe ndent preventing the realization of a successful correction algorithm. It was concluded that knee rotations other than flexion/extension may be affected with substantial errors when using skin markers. (C) 1997 Elsevier Science Ltd.