The Mechanical Relation between Chronic Ankle Instability and Pelvic Alignment: A Matched Case-Control Study

Background. Mechanical relation between the foot and pelvic alignment had been studied in healthy subjects and individuals with other musculoskeletal disorders; however, in chronic ankle instability (CAI), it has not yet been determined. Objectives. To investigate the difference in pelvic torsion (PT) among individuals with CAI and uninjured subjects and correlate PT with perceived ankle instability sensation and giving way episodes. Methods. This matched case-control study was performed on fifteen participants with unilateral CAI and 30 matched controls. All participants with CAI scored ≤ 24 on the Cumberland Ankle Instability Tool. The control participants were sex- and dominance limb-matched to the CAI group. A pelvic inclinometer and 10-cm visual analog scale were used for measuring PT and perception of ankle instability, respectively. The Mann–Whitney U-test and Pearson correlation coefficient were used for statistical analysis. Results. A statically significant difference in PT was observed between CAI participants and controls (P < 0.05) with a large clinically meaningful difference (effect size = 1.12). However, no significant (P > 0.05) relationships were observed between PT and perceived ankle instability or giving way episodes. Conclusion. Patients with unilateral CAI appear to have PT as a proximal strategy to maintain the proximal stable base and compensate for distal ankle instability. The clinically detectable difference in PT helps clinicians be aware of the chronic maladaptations in CAI. Additional studies are needed to investigate other lumbopelvic impairments affecting pelvic kinematics and ankle stability.