TITLE: Vertical Impact Increase in Middle Age May Explain Idiopathic Weight-bearing Joint Osteoarthritis 2001-1.pdf
Purpose: To test the hypothesis that ground reaaction force increases with age - an explanation of idiopathic osteoarthritis of the hip in humans.
Synopsis: Ground reaction force was measured while subjects performed a standard stepping task in young and older subjects. Ground reaction force when stepping was found to increase with advanvcing years. This increase may be explained by decline in plantar tactile sensibility. This may lead to impaired postural stability and behavior that amplifies impact in relation to instability.
Significance: This was the first report to show increase in vertical impact with advancng years. It may help explaining the rise in idiopathic hip osteoarthritis that occurs in late middle age. Specifically, stability in humans declines in humans after 40 years of age, at which time the incidence of osteoarthritis of the hip tends to increase. Also, there is some evidence that the incidence of osteoarthritis of the hip is lower in certain populations such as rural Jamaicans as ascertained in the mid-twentieth century, who spent most to their life barefoot. The increase in instability associated with aging causes compensatory behavior which amplifies impact. This elevated impact may explain the rapid increase in hip osteoarthritis that occurs in middle age. Further, improved stability associated with barefoot weight-bearing may be associated with attenuated impact. This may explain the lower incidence of hip osteoarthritis in barefoot populations.