Severity of functional and mechanical ankle instability in an active population

The purpose of this investigation was to evaluate the relationship between the severity of functional and mechanical ankle instability in physically active individuals.

Eighty college aged physically active individuals from a large university were recruited for this study. All subjects had unilateral functional ankle instability (FAI). FAI was defined as a history of at least two ankle sprains and a score less than or equal to 27 on the Cumberland Ankle Instability Tool (CAIT). The contralateral limb had no history of ankle injury or instability. Anterior displacement (mm) and talar tilt (degrees) were measured using the LigMaster joint arthrometer to identify mechanical ankle instability(MAI). Individuals were tested bilaterally and the maximum value attained during talar tilt and anterior displacement was used for statistical analysis.

First we evaluated side-to-side differences in MAI in all subjects. We found no significant difference between the FAI and the non-FAI ankle for anterior displacement (t(1.79)=1.66, p = 0.10) or talar tilt (t(1.79)=-0.07, p=0.95). Secondly, we evaluated the relationship between the FAI and MAI measures and found no significant correlations between the severity of FAI and magnitude of anterior displacement(r=0.18, p=0.12) or talar tilt (r=0.09, p=0.42).

This study demonstrated there was no side-to-side difference in MAI in individuals with unilateral functional ankle instability. Similarly, we also conclude there was no significant relationship between the severity of FAI and MAI. We feel that these findings suggest the symptoms of FAI may not be related to ankle joint laxity, but instead due to other factors associated with FAI.