Sex differences in dynamic joint stiffness during walking in older adults

Area of Science:

• Biomechanics
• Gerontology
• Orthopedics

Background:

• Knee osteoarthritis (OA) disproportionately affects older women.
• Walking assistance devices, like knee braces, aim to mitigate knee stress and prevent OA.
• Dynamic Joint Stiffness (DJS) quantifies assistive device resistance, crucial for objective stiffness prescription.

Purpose of the Study:

• Investigate sex-based differences in lower limb DJS during walking in older adults.
• Determine if DJS varies between older men and women in the sagittal plane.
• Establish a foundation for sex-specific recommendations for walking assistance.

Main Methods:

• Analyzed data from 132 healthy older adults (65+ years; 71 men, 61 women).
• Measured DJS of hip, knee, and ankle joints during the stance phase's power absorption.
• Compared DJS, joint excursion, and joint moments between sexes using Mann-Whitney U test and calculated effect size (r-value).

Main Results:

• Older women showed significantly lower ankle DJS and reduced ankle plantarflexion moment compared to men (p < 0.001, r = 0.35-0.42).
• Knee DJS was also lower in older women (p = 0.007), but with a small effect size (r = 0.24) as joint excursion and moment showed no significant differences.
• No significant sex differences were found in hip DJS (p = 0.703).

Conclusions:

• Reduced ankle plantarflexion moment likely causes lower ankle DJS in older women, indicating a need for ankle support.
• Observed differences in knee DJS do not currently explain the higher incidence of knee OA in older women.
• Findings highlight potential sex-specific considerations for assistive device prescription in older adults.