Abstract
The purpose of this study was to determine the movement of the center of pressure (COP) during a sit-to-stand (STS) motion at various angles of the knee joint and to identify a correlation between STS motion and COP. The subjects were ten healthy adults (mean age 27.0±3.4 years) . The movement of COP during STS motion was measured in each setting of 80°, 90° and 100° of knee flexion with hip flexion at 90° using a foot pressure measurement system (F-SCAN) . The movement and the track of COP were statistically analyzed. The motion of COP consisted of mainly an anterior-posterior sway and a slight lateral sway. The results showed a pattern in which COP moved posteriorly at the beginning of STS motion, reached a turning point then moved rapidly anteriorly and finally stopped. The turning point of COP showed a relation with the flexion angle of the knee at the beginning of STS motion and was located more posteriorly when the flexion angle became smaller. The maximum distance of lateral sway and the flexion angle of the knee were not significantly related even when the angle was altered. The anterior-posterior sway and the lateral sway of COP were considered to correspond to the dynamic function (mobility) and the static function (fixation) of the knee and ankle joints, respectively. The analysis of COP provides a reliable evaluation for STS motion ; therefore, a constant and stable movement of COP indicates secure performance of STS.
