title: Ankle ligament laxity and stiffness in chronic ankle instability.
abstract: BACKGROUND
  The contribution of mechanical laxity and ligament stiffness to chronic ankle instability is unclear, particularly when using the inversion laxity test, and may have implications for diagnosis, prognosis, and treatment. Our purpose was to determine if individuals with chronic ankle instability demonstrate greater mechanical ligament laxity and altered stiffness compared to controls and copers (those with a healed sprain) during an instrumented arthrometer inversion stress test.
  
  
  METHODS
  Recreationally active individuals were classified as those with chronic ankle instability (n = 16), copers (n = 16), or controls (n = 16) based on injury history and self-reported score on the Cumberland Ankle Instability Tool (CAIT). Three trials of an inversion stress test were applied with an instrumented arthrometer utilizing a reliable tester. Talocrural inversion (degrees) and stiffness values were extracted. One-way ANOVAs were calculated, and Tukey post hoc testing was applied (α ≤ .05).
  
  
  RESULTS
  Groups were not different in age, height, or weight. The chronic ankle instability group (19 ± 6) had significantly lower CAIT scores than the control (30 ± 1) and coper (29 ± 1) groups (P < .001). The chronic ankle instability group (23 ± 12 degrees) demonstrated significantly greater inversion than the controls (13 ± 9 degrees) (P = .04) but was not significantly different than the copers (17 ± 10 degrees). No significant differences were detected in stiffness between the groups.
  
  
  CONCLUSIONS
  The chronic ankle instability group demonstrated decreased self-reported ankle function and increased mechanical laxity utilizing an instrumented arthrometer for inversion compared to the control group but not the coper group. Laxity, but not stiffness, may be a factor affecting chronic ankle instability and self-reported function.
  
  
  METHODS
  Level III, comparative study.
authors.affiliation: Biomechanics Laboratory, Department of Kinesiology, University of Georgia, Athens, Georgia, USA browncn@uga.edu.
authors.forename: Cathleen N
authors.initials: CN
authors.lastname: Brown
authors.affiliation: Biomechanics Research Building, School of Health, Physical Education and Recreation, University of Nebraska, Omaha, Nebraska, USA.
authors.forename: Adam B
authors.initials: AB
authors.lastname: Rosen
authors.affiliation: Biomechanics Laboratory, Department of Kinesiology, University of Georgia, Athens, Georgia, USA.
authors.forename: Jupil
authors.initials: J
authors.lastname: Ko
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000503:physiopathology*; D053587:Arthrometry, Articular; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000503:physiopathology*; D008297:Male; D055815:Young Adult
keywords: arthrometer; coper; inversion