Relationship Between Functional And Mechanical Ankle Instability In Physically Active Individuals

Abstract

Individuals suffering lateral ankle sprains can develop functional ankle instability (FAI) and/or mechanical ankle instability (MAI). While some consider these to be two separate entities under the umbrella of chronic ankle instability, the relationship between FAI and MAI remains unclear. PURPOSE: The purpose of this investigation was to evaluate the relationship between functional and mechanical ankle instability in physically active individuals. METHODS: Eighty college aged physically active individuals (male=50, female=30, 19.81±1.42yrs, 176.5±9.9cm, 74.77±15.31kg) from a large Division 1 institution were recruited for this study. All subjects had unilateral FAI. FAI was defined as a history of at least two ankle sprains and a score of less than or equal to 27 on the Cumberland Ankle Instability Tool (CAIT). The contralateral limb had no history of ankle injury. Anterior displacement(mm) and talar tilt(°) testing was performed using a joint arthrometer to measure MAI. Individuals were tested bilaterally and the maximum value attained during talar tilt and anterior displacement was used for statistical analysis. Dependent t-tests were used to compare the anterior displacement and talar tilt between the FAI and uninjured ankle. Two Pearson product moment correlations were used to examine the relationship between FAI and MAI, one for anterior displacement and one for talar tilt. RESULTS: We found no significant difference between the FAI and uninjured ankle for anterior displacement (t1,79 = 1.66,p =.10) or talar tilt (t1.79 = -.07, p =.95). Additionally, no significant correlations were identified between the CAIT score for the FAI limb and anterior displacement(r =.18, p =.12) or talar tilt (r =.09, p =.42). CONCLUSION: Functional and mechanical ankle instability appears to be two discreet entities. This study suggests FAI can occur independently from MAI. In addition, individuals with a greater degree of FAI do not possess more MAI.