Age and passive ankle stiffness in healthy women

The purpose of the study was to evaluate passive joint stiffness in ankles of young (aged 21-40 years; n = 15), middle-aged (aged 41-60 years; n = 15), and young elderly (aged 61-80 years; n = 15) women. The effect of knee position on passive joint stiffness was also evaluated by testing the subjects with the knee flexed (90 degrees) and with the knee extended (0 degrees). A torque motor system was used to record angular displacement and resistive torque during a 6 degrees/sec ankle rotation from 10 degrees of plantar flexion to 10 degrees of dorsiflexion (DF). Passive torque and passive elastic stiffness were measured at 0, 5, and 10 degrees of DF. Both measures increased nonlinearly as the ankle was rotated into DF, but showed no significant differences between the three age groups tested. There was also no significant difference in the passive stiffness measurements when the knee was flexed or extended. We concluded that within the range of motion tested, the factors of age and knee position do not affect the passive stiffness observed in the ankle joints of healthy women. We have now established baseline values of passive ankle joint stiffness for healthy women during DF within a functional ROM, which will be useful in the clinical evaluation of passive ankle joint stiffness and in studies where treatment efficacy is being investigated.