Investigation of the Method of Measuring the Pattern of Pelvic Bone Motion Using Skin Markers during Sit-to-stand Task

[Purpose] The validity of the measurement of the direction of pelvic motion using a 3D motion analysis with skin markers during a sit-to-stand task was determined. [Participants and Methods] Fifteen healthy subjects were recruited and the motion of 30 sacroiliac joints in total were captured during the task. The markers on the skin surfaces of bony landmarks of the pelvis were set in a relaxed seated position and in the position just before seat-off. The angle of the innominate motion relative to the sacrum was calculated from the initiation of the task to the instant of seat-off and compared between the two conditions. [Results] In the 2 conditions, the direction of sacroiliac motion coincided in all joints. [Conclusion] The results suggest that in order to determine the direction of sacroiliac motion a procedure applying the markers on the skin surface in a seated position can be used to study sit-to-stand movement.