Kinematic adaptations to a variable stiffness shoe: mechanisms for reducing joint loading.

Area of Science:

• Biomechanics
• Orthopedics
• Gait Analysis

Background:

• Medial-compartment knee osteoarthritis is often treated with interventions that modify load.
• Variable-stiffness shoes can reduce knee adduction moment and pain, but the underlying gait modification mechanisms are unclear.
• Understanding these mechanisms is crucial for developing effective load-modifying treatments.

Purpose of the Study:

• To investigate differences in frontal plane kinematics, ground reaction forces (GRFs), and center of pressure (COP) between variable-stiffness and constant-stiffness shoes.
• To test the hypothesis that these differences correlate with reduced knee adduction moment.

Main Methods:

• Principal component analysis (PCA) was applied to gait data from eleven healthy adults walking in both shoe types.
• Data included frontal plane kinematics, GRFs, and COP measurements.
• PCA identified key gait patterns differentiating the two shoe conditions.

Main Results:

• Significant differences in frontal plane gait patterns were observed between the variable-stiffness and control shoes.
• The variable-stiffness shoe promoted increased ankle eversion and knee abduction/adduction, alongside decreased hip adduction and pelvic obliquity.
• Reduced COP excursion and peak medial-lateral GRFs were noted with the variable-stiffness shoe.

Conclusions:

• Variable-stiffness shoes induce unique dynamic frontal plane changes in the ankle, hip, and pelvis.
• These changes alter GRF and COP, leading to a reduced knee adduction moment during gait.
• This suggests a novel mechanism for load modification in knee osteoarthritis treatment, distinct from fixed interventions.