The purpose of the study was to explore differences in the coronal biomechanics of the trunk, pelvis, hip, and knee joints, and gluteus medius muscle activity (GMed) during walking and step down from two riser heights. Joint kinematics and kinetics from 20 healthy participants were recorded using a 10-camera Qualisys system and force plates, and GMed EMG was recorded using a Delsys Trigno system. Hip abductor strength was measured using a hand-held dynamometer. Pelvic obliquity and lateral trunk bending excursions were significantly higher in walking than in step-down tasks. Significantly greater knee adduction moments were seen during both step-down tasks compared to level walking with significantly greater GMed activity.
The hip abductor muscles have been identified as the most important muscles to control and stabilize the pelvis during locomotion. The Gluteus Medius (GMed) muscle plays a key role in controlling the coronal pelvic motion and any functional impairment of this muscle can lead to excessive lateral trunk bending, which can be observed in people with a variety of knee problems including knee OA and PFP . Chang et al. proposed that coronal plane movement impairment in people with GMed weakness includes ipsilateral trunk bending and contralateral pelvic drop during stance, which is also a mechanism that increases the loading on the medial compartment of the knee.