Rectus femoris hyperreflexia contributes to Stiff-Knee gait after stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomechanics

Background:

• Stiff-Knee gait (SKG) after stroke is characterized by reduced knee flexion during the swing phase.
• Excessive quadriceps activation is a hypothesized cause of reduced knee flexion in SKG.
• The role of quadriceps hyperreflexia in this excessive activation remains unclear.

Purpose of the Study:

• To investigate the relationship between quadriceps hyperreflexia and knee flexion angle during walking in individuals with post-stroke SKG.
• To determine if spinal reflex excitability contributes to the motor deficits observed in SKG.

Main Methods:

• Recorded the rectus femoris (RF) H-reflex in 10 participants with post-stroke SKG and 10 healthy controls during standing and walking.
• Healthy participants voluntarily increased quadriceps activity using EMG feedback to assess the impact on RF H-reflex.
• Analyzed the correlation between RF H-reflex amplitude and knee flexion angle.

Main Results:

• A significant negative correlation was found between RF H-reflex amplitude and knee flexion angle in post-stroke SKG (R = -0.92, p = 0.001).
• In healthy controls, RF H-reflex amplitude was not correlated with knee flexion angle, regardless of voluntary quadriceps activation.
• RF H-reflex modulation between standing and walking was impaired in individuals with post-stroke SKG compared to controls.

Conclusions:

• Impaired rectus femoris reflex modulation is a key feature of post-stroke SKG.
• Quadriceps hyperreflexia appears to play a significant role in limiting knee flexion during walking in SKG.
• Therapeutic strategies targeting quadriceps hyperreflexia may improve knee joint function in stroke survivors with SKG.