title: Mechanical instability destabilises the ankle joint directly in the ankle-sprain mechanism.
abstract: BACKGROUND
  Despite massive research efforts, it remains unclear how mechanical ankle instability (MAI) and functional ankle instability (FAI) affect joint control in the situation of ankle sprain. Thus, the purpose of this study was to evaluate whether individuals with MAI have deficits in stabilising their ankle joint in a close-to-injury situation compared with those with FAI and healthy controls.
  
  
  METHODS
  Ankle-joint control was assessed by means of three-dimensional motion analysis and electromyography in participants with FAI and MAI (n=19), in participants with pure FAI (n=9) and in healthy controls (n=18). Close-to-injury situations were simulated during standing, walking and jumping by means of a custom-made tilt platform.
  
  
  RESULTS
  Individuals with FAI and MAI displayed significantly greater maximum ankle inversion angles (+5°) and inversion velocities (+50°/s) in the walking and jumping conditions compared to those with pure FAI and controls. Furthermore, individuals in the FAI and MAI group showed a significantly decreased pre-activation of the peroneus longus muscle during jumping compared to those with FAI. No differences between groups were found for plantar flexion and internal rotation, or for muscle activities following tilting of the platform.
  
  
  CONCLUSIONS
  The present study demonstrates that MAI is characterised by impairments of ankle-joint control in close-to-injury situations. This could make these individuals more prone to recurrent ankle sprains, and suggests the need for additional mechanical support such as braces or even surgery. In addition, the study highlights the fact that dynamic experimental test conditions in the acting participant are needed to further unravel the mystery of chronic ankle instability.
authors.affiliation: Department of Sport and Sport Science, University of Freiburg, , Freiburg, Germany.
authors.forename: Dominic
authors.initials: D
authors.lastname: Gehring
authors.forename: Katrin
authors.initials: K
authors.lastname: Faschian
authors.forename: Benedikt
authors.initials: B
authors.lastname: Lauber
authors.forename: Heinz
authors.initials: H
authors.lastname: Lohrer
authors.forename: Tanja
authors.initials: T
authors.lastname: Nauck
authors.forename: Albert
authors.initials: A
authors.lastname: Gollhofer
mesh_terms: D016512:Ankle Injuries / Q000209:etiology* / Q000503:physiopathology; D001265:Athletic Injuries / Q000209:etiology* / Q000503:physiopathology; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D002908:Chronic Disease; D004576:Electromyography; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000150:complications* / Q000503:physiopathology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D055815:Young Adult
keywords: Ankle injuries; Biomechanics; Gait analysis