Factors Associated with Functional Ankle Instability in Physically Active Young Adults

Functional ankle instability (FAI) is a clinical syndrome characterized by perceived ankle unsteadiness or pain while performing weight bearing activities or sport participation. FAI can limit a person’s ability to perform activities of daily living, decrease their level of physical activity across their life span, and reduce their quality of life. Although many studies have attempted to identify the impairments associated with FAI, there is no clear consensus in the literature. That may be because the studies vary widely in their methodologies and some of them did not account for limb dominancy. Additionally, there is no model for FAI to subgroup the different impairments found in subjects with FAI.

We examine the impairments associated with FAI comparing cases to healthy controls. We found that subjects with FAI were more impaired than controls, and there were differences between the dominant and non-dominant limbs. For example, on the dominant limb the FAI subjects had less hip abduction power, which we believe it was the reason they had less dynamic balance in posteromedial direction of the Star Excursion Balance Test (SEBT). 

We look at the causes and consequences of FAI in physically active young adults.  We propose an FAI model to subgroups subjects with FAI. We find that gender, history of lateral ankle sprain (LAS), recurrent LAS and BMI may be considered risk factors for FAI on both limbs. Our FAI model showed that 28.1% of ankles with FAI of our sample had FAI without the history of LAS, which supported the assumption that FAI can occur without having history of LAS.

We examine factors affecting dynamic balance measured by SEBT. A novel finding of this study is that eversion ROM has a moderate correlation with the posterolateral direction of the SEBT of the dominant limb. We also found that an increase BMI or the more LASs subjects had, the worse their dynamic balance the anterior direction of the SEBT.

Chapter five summarizes the findings and discuss the clinical relevance of these findings and the study limitations.