Trunk and lower limb kinematic alterations during the forward step-down task in women with multiple sclerosis: a comparative 3D motion analysis.

Abstract

Background: The forward step-down (FSD) task is a fundamental daily movement requiring coordinated trunk and lower limb control. Individuals with Multiple Sclerosis (MS) often experience neuromuscular impairments that may alter movement patterns during such functional tasks. This study aimed to investigate and compare trunk and lower limb kinematics during the FSD task in women with and without MS.

Methods: Thirty-six women aged 20 to 40 years participated in the study, including 18 with relapsing-remitting MS (EDSS scores ranging from 1 to 4.5) and 18 healthy controls matched for age, anthropometric measures, and sex. Three-dimensional kinematic data of the trunk and lower limbs were recorded at 120 Hz using a Vicon motion capture system during the FSD task performed from a 16 cm platform. Key events were defined at 60° knee flexion and at maximum knee flexion. Joint angles in the sagittal, frontal, and transverse planes were extracted for the ankle, knee, hip, and trunk. Independent-samples t-tests were used to compare the two groups.

Results: Significant kinematic differences were observed between groups. At 60° of knee flexion, the MS group exhibited increased ankle external rotation (P = 0.009) and greater trunk flexion (P = 0.001). At maximum knee flexion, the MS group demonstrated increased ankle external rotation (P = 0.029), reduced knee flexion (P = 0.001), decreased knee internal rotation (P = 0.01), greater hip adduction (P = 0.002), and increased trunk flexion (P = 0.001). These findings indicate altered multi-joint coordination and compensatory strategies in participants with MS.

Conclusion: Women with MS exhibit distinct kinematic deviations in the trunk and lower limbs during the FSD task, reflecting neuromuscular deficits and compensatory adaptations. These alterations highlight the importance of targeted rehabilitation strategies that focus on trunk control, hip stabilization, and lower limb strength and dynamic alignment to enhance functional performance and reduce fall risk in this population.