Fig. 1.

Shows the markers placed on boney landmarks of the pelvis. Top left picture shows the anterior view of a subject with two markers on the ASIS and top right picture shows the posterior view of two markers placed on the PSIS and the cluster of three markers attached to the sacrum. For the Traditional set four anatomical markers are used to track the motion (two black circles = left/right ASIS and two light blue circles = left/right PSIS are shown on the skeleton) while for the Cluster method, a separate cluster positioned on sacrum is used for tracking the pelvic movement which is shown by blue colour on the bottom left picture. Coordinate frame of the pelvis is in red. Pelvic tilt represents the movement of the pelvis around the X axis (flexion/extension), pelvic obliquity shows the movement of the pelvis around the Y axis (Abduction/adduction), and finally pelvic rotation stands for the movement of the pelvis around the Z axis. The origin of the segment is defined as the midpoint between two ASIS, X axis defined as a line parallel to the ASIS () and the Y axis is defined as a line connecting the midpoints of ASIS and PSIS (- - - - - -). The Z axis is orthogonal to other two axes. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)