2021 CMSC Annual Meeting

Difference in Lower Limb Strength Asymmetry between Fallers and Non-Fallers with Multiple Sclerosis


Background: Lower limb (LL) asymmetry in persons with multiple sclerosis (PwMS) has been associated with decreased balance and abnormal temporal spatial parameters, which may lead to increased risk of falls. To date there have been no studies in PwMS that compare the LL strength asymmetry between known fallers and non-fallers.
Objectives: 1) To determine whether there is a difference in LL strength asymmetry between fallers and non-fallers in PwMS, and 2) to identify a cut-off asymmetry score and its odds for increased fall-risk after controlling for age and gender.
Methods: A total of 151 PwMS were included in this preliminary analysis of an ongoing, larger study. LL strength of knee flexion and extension, ankle plantar flexion and dorsiflexion, and hip abduction, flexion and extension was collected as peak torque (Newton-meters; Nm). Asymmetry was calculated as (stronger limb-weaker limb)/stronger limb x 100. PwMS were characterized as a faller if they self-reported >1 fall in the past six months. Differences in age, gender, disease duration, Patient Determined Disease Steps (PDDS), and LL strength were compared between fallers (n=86) and non-fallers (n=65). Optimal cut-offs of LL strength asymmetry were determined using the Youden index. The asymmetry cut-off scores were then entered into a logistic regression, with faller status as the outcome, with age and gender as covariates.
Results: There were no differences in age, gender, or disease duration; however, fallers had higher median PDDS scores (p<0.001). Only asymmetry of knee extension (p=0.010) and flexion (p=0.019) were different between fallers and non-fallers. After controlling for age and gender, the odds of having a fall was 2.75 times higher among PwMS who had an asymmetry of 18.44% or greater in their knee extension compared to PwMS with a lower level of asymmetry (95% CI: 1.38, 5.45, p = .004). Although an asymmetry of 14.98% or greater was determined to be the optimal cut-off for knee flexion, it did not significantly predict fallers after controlling for age and gender (OR: 1.84, 95% CI: 0.96, 3.55, p = .068). Conclusions: The findings of this study demonstrate that knee extension strength asymmetry of over 18.44% increases the odds of having a fall among PwMS. These results suggest reducing knee extensor strength asymmetry between knee extensors may reduce fall risk in PwMS.