Quantifying Intrinsic Ankle Stiffness in Quiet Standing: A Systematic Review

Abstract

Introduction: Ankle stiffness is a factor that contributes to maintaining balance and counteracts the forces of gravity as the body sways. Stability while standing quietly depends on its value. Intrinsic ankle stiffness refers to (i) the passive resistance provided by the structural components of the ankle joint itself, such as the ligaments and joint capsules, (ii) a property of the joint that remains constant regardless of the external forces applied, (iii) a characteristic that affects the stability and control of the ankle joint. The aim is to present compilation of the results published in the researchers’ work makes it possible to analyze changes in the value of ankle stiffness for perturbations of different amplitude. Material and Methods: The review is based on articles identified through searches of Pubmed, Web of Science, and Scopus. There were no restrictions on the publication date. The Boolean search strategy was used. Results: Ankle stiffness changes with increasing sway amplitude. Its values are greater for perturbations of smaller amplitudes and, therefore, cannot be represented by a single value. Passive stiffness reduces sway and allows time for the active system to respond. The interaction of these two mechanisms ensures the stability of an upright posture. Conclusions: Ankle stiffness is a parameter that can be applied in clinical practice. The exact determination of the range of stiffness values is a useful tool to define a motor organization/reorganization.