Loading rate during weight acceptance: Differential contributions of the knee and contralateral ankle with aging.

BACKGROUND

An increase in impact loading is associated with the risk of knee osteoarthritis (OA). Dynamic joint stiffness (DJS), defined as the slope of the joint moment-angle relationship during power absorption phase, reflects the joint's power absorption characteristics.

RESEARCH QUESTION: Do the relationships between loading rate (LR) and knee DJS of loading limb, as well as ankle DJS of trailing limb, differ between younger and older adults?

METHODS

The AIST Gait Database 2019 included 129 older adults and 107 younger adults walking at a self-selected speed. LR was defined as the first vertical ground reaction force peak divided by the time from initial contact. Knee and ankle DJS were computed in the sagittal plane during power absorption intervals. Group differences were tested, and within-group regressions predicted LR from DJS and joint angular excursions and joint moment impulses at both joints, with covariates.

RESULTS

Older adults had significantly lower knee DJS and extension moment impulse and higher knee flexion excursion. The ankle dorsiflexion excursion and plantar flexion impulse was significantly smaller in older adults, while ankle DJS were similar between groups. In older adults, LR was negatively associated with knee DJS. In younger adults, LR was negatively associated with ankle DJS and plantar flexion excursion, and positively associated with knee DJS.

SIGNIFICANCE: Age-related differences in shock absorption may reflect changes in the relative contributions of the knee and ankle, and these findings may help inform future prevention and rehabilitation strategies targeting both joints.