Meeting Abstract
Hip osteoarthritis (OA) is one of the most common joint diseases. This disorder causes OA patients to alter their gait to compensate for hip pain while maintaining frontal plane balance during walking. These compensatory gaits are likely an attempt to minimize hip abduction moment and/or muscle force. However, different compensatory characteristics exist among hip OA patients, particularly in pelvic motion, step width and muscle activity. Here we investigated the hip biomechanics underlying two compensatory gaits of hip OA: exaggerated pelvic drop and pelvic elevation on the swing side. We recorded full-body kinematics, kinetics and muscle activity in 9 subjects during normal and simulated pathological gaits. Kinematics were recorded via a 12-camera Vicon motion capture system using the Plug-In gait marker set. Subjects walked on an AMTI force-instrumented treadmill at 1.0 m/s under varying pelvic motions (normal, pelvic drop, pelvic elevation). Gluteus medius muscle activity was recorded using a Noraxon surface electromyography system. Compared to normal walking, exaggerated pelvic drop on the swing side entailed an increase in maximum hip abduction moment (~35%). Exaggerated pelvic drop on the swing side also elicited an increase in maximum stance-phase gluteus medius activity in our subjects. On the other hand, pelvic elevation resulted in a decrease in maximum hip abduction moment (~13%) though was accompanied by an increase in step width (~25%) and the highest increase in stance-phase gluteus medius muscle activity (~80%). Our results indicate that different OA gaits may optimize different gait characteristics. Pelvic elevation may be used when prioritizing hip abduction moment minimization, while exaggerated pelvic drop may be a solution to lower gluteal muscle force.
