Deficit in intersegmental torques drives post-stroke stiff-knee gait.

Area of Science:

• Biomechanics
• Neurorehabilitation
• Human Movement Science

Background:

• Stroke frequently impairs walking ability, necessitating adaptive gait strategies like hip hiking.
• Reduced knee flexion during the swing phase is a common post-stroke gait deficit.
• The underlying biomechanical causes of reduced knee flexion are complex and not fully understood.

Purpose of the Study:

• To investigate the role of intersegmental forces in causing reduced knee flexion post-stroke.
• To compare active muscle-generated and passive intersegmental torques between post-stroke and neurotypical individuals during walking.
• To identify specific biomechanical deficits contributing to impaired knee flexion.

Main Methods:

• Utilized subject-specific inverse modeling of body dynamics for overground walking analysis.
• Compared force generation and joint torques between post-stroke and neurotypical participant groups.
• Differentiated contributions of active muscle torques and passive intersegmental torques.

Main Results:

• Active knee torque generation was similar between post-stroke and neurotypical groups at swing onset.
• Knee interaction torque was identified as the primary cause of reduced knee flexion.
• A significant deficit in hip flexion torque generation was observed in the post-stroke group compared to the neurotypical group.

Conclusions:

• Reduced hip flexion torque at swing onset is a key biomechanical mechanism driving reduced knee flexion post-stroke.
• Intersegmental forces, particularly at the hip, play a critical role in post-stroke gait impairment.
• This finding provides a physics-informed target for developing effective post-stroke gait rehabilitation strategies.