Hysteresis and stiffness of the lateral ankle complex in those with chronic ankle instability.

The role of mechanical laxity and viscoelastic tissue properties in chronic ankle instability (CAI) is unclear, but may influence repeated injury. The purpose was to determine if lateral ankle complex stiffness and hysteresis was altered in CAI individuals with and without mechanical laxity, compared to copers and uninjured controls. Thirty-five recreational athletes (19 females, 22.1 ± 2.7 years, 69.7 ± 15.7 kg, 168.4 ± 10.7 cm) were assessed for ankle injury history and self-reported instability. An instrumented arthrometer was applied and laxity, stiffness and hysteresis values were captured. Results from ANOVA tests indicated the CAI with laxity group had lower beginning- (3.2 ± 0.6 N/mm) and end-range stiffness (4.5 ± 0.4 N/mm) than the CAI without laxity group (4.7 ± 0.6; 6.0 ± 0.6 N/mm) and uninjured controls (4.6 ± 1.1; 5.8 ± 0.8 N/mm, p < 0.003). Hysteresis was greater in the CAI with laxity group than without laxity (91.0 ± 17.3 vs 62.8 ± 12.0 dN•mm; p = 0.03). Altered tissue properties in a CAI with laxity group likely indicate diminished ability of the lateral ankle complex to respond to loading. Accurately assessing, then avoiding or restoring tissue impairments after injury, may encourage better patient outcomes.