Related Asymmetries in Achilles Tendon Stiffness and Ankle Mobility after Rupture

INTRODUCTION The Achilles tendon is one of the largest and strongest in the body, yet is most prone to unilateral spontaneous rupture in humans. This injury dramatically changes the tissue’s composition, which has a significant effect on its mechanical behavior [1] and presumably on ankle joint function. Earlier work has considered this particular relationship between the mechanical status and function of the Achilles tendon after post-rupture healing and attempted tissue regeneration. However, these were either limited to animal models [2] or indirect parameters of tendon stiffness, namely passive biomechanics of the plantarflexors [3]. Loss of plantarflexor muscle strength after Achilles tendon rupture has already been well documented [4], but the in vivo status of the regenerated tendon tissue has yet to be elucidated in human subjects. Thus the relationship between tendon stiffness and post-rupture ankle function may be an indicator of tissue regenerative status. We hypothesize that subjects with higher asymmetries in tendon stiffness will demonstrate similarly higher asymmetries in ankle mobility during gait.