Correlations among multiple measures of functional and mechanical instability in subjects with chronic ankle instability

Context: Although dozens of individual mechanical and functional insufficiencies have been reported in those with chronic ankle instability (CAI), no authors to date have examined the relationship of the insufficiencies to each other. Therefore, studying both the functional and mechanical insufficiencies in the same experimental design will provide valuable information. Objective: To determine the relationships among the numerous functional and mechanical insufficiencies purported to cause CAI. Design: Descriptive study with a correlational design. Setting: Medical center and research laboratory. Patients or Other Participants: Thirty subjects with unilateral CAI (15 males and 15 females: age = 20.3 +/- 1.3 years; height = 172.5 +/- 10.7 cm; mass = 72.9 +/- 15.8 kg). Main Outcome Measure(s): Twenty-six measures of mechanical insufficiencies (ankle laxity and hypomobility) and functional insufficiencies (subjective level of function, static and dynamic balance, ankle and hip strength) were taken on both limbs of all subjects. Bivariate correlations using Pearson product moment coefficients were calculated between all dependent variables measured in the unstable ankles. The level of significance was set a priori at P <= .05 for all analyses. Results: A number (35) of significant bivariate correlations were identified. Most (32) of these significant relationships were found between functional instability measures (r =.38 to.96). Three significant relationships were noted between measures of functional (balance, strength) and mechanical (laxity, hypomobility) instability (r =.47 to .52). No significant relationships were found between the different mechanical instability measures. Conclusions: Certain measures of functional instability were significantly correlated and may be redundant. Additionally, the significant correlations between measures of functional (balance, strength) and mechanical instability (laxity, hypomobility) demonstrate that the 2 factors are not completely dichotomous and need to be examined together.