Pelvifemoral kinematics while ascending single steps of different heights

Motion of the femur and pelvis during hip flexion has been examined previously, but principally in the sagittal plane and during nonfunctional activities. In this study we examined femoral elevation in the sagittal plane and pelvic rotation in the sagittal and frontal planes while subjects flexed their hips to ascend single steps. Fourteen subjects ascended single steps of 4 different heights leading with each lower limb. Motion of the lead femur and pelvis during the flexion phase of step ascent was tracked using an infrared motion capture system. Depending on step height and lead limb, step ascent involved elevation of the femur (mean 47.2 degrees to 89.6 degrees) and rotation of the pelvis in both the sagittal plane (tilting: mean 2.6 degrees to 9.7 degrees) and frontal plane (listing: mean 4.2 degrees to 11.9 degrees). Along with maximum femoral elevation, maximum pelvic rotation increased significantly (p<.001) with step height. Femoral elevation and pelvic rotation during the flexion phase of step ascent were synergistic (r=.852-.999). Practitioners should consider pelvic rotation in addition to femoral motion when observing individuals' ascent of steps.