Relative changes in ankle and hip control during bilateral joint movements in persons with multiple sclerosis

Abstract

Objective: The purpose of this study was to quantify hip and ankle impairments contributing to movement dysfunction in multiple sclerosis (MS).

Methods: Volitional phasing of bilateral hip and ankle torques was assessed using a load-cell-instrumented servomotor drive system in ten participants with MS and 10 age-matched healthy participants. The hips and ankles were separately bilaterally oscillated 180° out of phase (40° range of motion) at a frequency of 0.75 Hz while the other joints were held stationary. Participants were instructed to assist in the same direction as the robot-imposed movement. The hip and ankle torques were measured and work was calculated for each movement.

Results: Total negative work at the ankle was significantly different between groups (p=0.040). The participants with MS produced larger negative work during hip flexion (p=0.042) and ankle flexion (p=0.037). Negative work at the hip was significantly correlated with the Berg Balance Scores and Timed 25 Feet Walk Test, and trends demonstrated increasing negative work with increasing clinical impairment in MS.

Conclusions: These results suggest an increased importance of the hip in functional balance and gait in MS.

Significance: Rehabilitation strategies targeting ankle recovery or compensation using the hip might improve movement function in MS.

Keywords: Coordination; Joint moment; Negative work; Robot.