Correlations Among Multiple Measures of Functional and Mechanical Instability in Subjects with Chronic Ankle Instability (Original Research) (Report‪)‬

Chronic ankle instability (CAI) has been reported to occur in approximately 31% to 40% of people with a previous history of a lateral ankle sprain (1,2) and describes the occurrence of repetitive bouts of lateral ankle instability. (3) Numerous ankle sprains and a subjective feeling of the ankle "giving way" result. These chronic symptoms limit the patient in both activities of daily living and athletic activity. Two primary causes of CAI have been deemed responsible: mechanical ankle instability (MAI) and functional ankle instability (FAI). (3-5) A variety of insufficiencies that lead to each type of instability have been identified in those with CA1. Mechanical insufficiencies include pathologic laxity, impaired arthrokinematics, and synovial and degenerative changes. (3,6) Functional insufficiencies include impaired proprioception, altered neuromuscular control, strength deficits, and diminished postural control. (3) Despite the fact that dozens of individual mechanical and functional insufficiencies have been reported in those with CAI, no authors have examined the relationship of multiple measures of these insufficiencies to each other. Therefore, examining both the functional and mechanical insufficiencies of CAI together in the same experimental design will provide important information. Previous researchers (4,5,7-13) examining ankle instability have focused on identifying differences between individuals with and without CAI. Mechanical and functional instability are often seen as 2 dichotomous causes of CAI. Although a relationship between MAI and FAI has been suggested, (3,5,7) we do not currently know what this exact relationship is. The aforementioned groups (3,5,7) did not compare the different measures of FAI and MAI statistically. Additionally, we do not know what the relationship is within the measures of FAI and MAI. For example, if a patient has a deficit in one FAI measure, can we assume he or she also has deficits in other FAI measures as well? Also, are MAI and FAI truly dichotomous? By understanding these relationships, we can make more informed clinical decisions regarding which exercises would best help a particular patient without having to test or examine for all possible insufficiencies. Scientifically, by better understanding these relationships, we improve our knowledge of the relationships among the different measures related to CAI and make better decisions as to which variables should be examined in future research projects.