Effects of Disability on Lower Extremity Joint Contributions and Total Support Moment in Individuals with Multiple Sclerosis

Background: Various connections between gait characteristics and patient outcomes of multiple sclerosis (MS) have become common research topics, authenticating the popularity of using gait analysis for functional status evalution of MS patients. However, the intra-limb kinetic synergy of the lower extremity joints of these individuals during walking is less understood. This focus area utilizes total support moment (TSM) and ancillary variables including moment impulse and joint contributions. These parameters have proven themselves valuable to several functional impairment topics and possess the potential to help elucidate the link between MS disability classifications and gait.

Objectives: To conduct a preliminary analysis of the effects of disability on lower extremity joint contributions to TSM and TSM impulse among MS patients.

Methods: Six MS patients with EDSS scores between 1.0 and 6.0 participated in this study (age=49±9.99 years;  height=1.64±0.12 m, weight=74.7±20.4 kg).  Patients were separated into three groups based on the level of disability indicated by their EDSS score (Group 1 [low level]= EDSS 1.0-2.5, Group 2 [moderate level]=EDSS 3.0-4.5, and Group 3 [high level]= EDSS 5.0-6.0). Motion capture and force-plate data were collected simultaneously during walking trials to compute TSM from the sum of the sagittal plane ankle, knee, and hip joint moments.  Time integration of these moments over the stance duration yielded corresponding moments impulses. The percentages of ankle, knee, and hip joint moment impulse included within TSM impulse were then generated to represent each joint’s contribution. Differences between groups for joint contributions and TSM impulse were investigated using a Kruskal-Wallis Test was conducted (α=.05).

Results: The only significant difference between groups came from knee joint contribution, H(2)= 13.413, p= .001, with a mean rank of 40.74 for Group 1, 20.50 for Group 2, and 29.35 for Group 3. According to the pairwise comparisons for this variable, the only statistically significant difference was between Group 1 and Group 2, H(2) = 29.238, p= .001.

Conclusions: MS patients with a low level of disability exhibit gait characteristics most similar to, if not indistinguishable from, typical gait characteristics. In this study, these patients demonstrated significantly higher knee joint contributions than the moderate group, which parallels research evidencing that healthy individuals have higher knee contributions than individuals with functional impairments.  Conversely, the abundant similarities between groups for the other contributions and TSM suggest that patients with different levels of disability may have rather similar control strategies during walking. Further research on joint contributions within a larger sample along with control subjects is needed to better understand the effect of disability on bodyweight support mechanisms in this population.