title: Relationship between functional ankle instability and postural control.
abstract: METHODS
  Controlled laboratory study using a cross-sectional design.
  
  
  OBJECTIVE
  To investigate the relationship between postural control and functional ankle instability during a hop-landing task, and to investigate whether postural control is altered in people with functional ankle instability.
  
  
  METHODS
  Sixty volunteers classified by the Cumberland Ankle Instability Tool (CAIT) scores formed the external control group (CAIT score, >or= 28, n = 31) and the instability group (CAIT score, <or= 27 and history of at least 1 ankle sprain; n = 29). Postural control was measured with the landing test, in which participants stood on 1 lower extremity for 3 seconds on a step, then hopped down onto a force plate and regained postural stability after landing. The main outcome measurements were time to stability (TTS) after landing for ankle inversion, dorsiflexion, and summated electromyographic (EMG) signal amplitude for the tibialis anterior, soleus, and fibularis longus. The secondary outcomes were the proportion of movement in the frontal plane for hip and ankle, the variability of inversion movement prior to hopping, and the variables from ground reaction force.
  
  
  RESULTS
  There were no associations (P > .05) between the CAIT scores and the TTS for ankle inversion (r = -0.25), dorsiflexion (r = -0.04), summated EMG (r = -0.13) and proportion of movement in the frontal plane (r = 0.005). Participants in the instability group took longer to regain stability in inversion and displayed greater inversion variability prejump than the control group (P = .05 and .009, respectively).
  
  
  CONCLUSIONS
  Ankle inversion control is affected in people with functional ankle instability in tasks of postural control after landing from a hop.
authors.affiliation: School of Physiotherapy, The University of Sydney, Australia. made6338@usyd.edu.au
authors.forename: Marcos
authors.initials: M
authors.lastname: de Noronha
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Refshauge
authors.forename: Jack
authors.initials: J
authors.lastname: Crosbie
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Kilbreath
mesh_terms: D000293:Adolescent; D000328:Adult; D016512:Ankle Injuries / Q000209:etiology / Q000503:physiopathology*; D000843:Ankle Joint / Q000473:pathology*; D003430:Cross-Sectional Studies; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D004856:Postural Balance; D011187:Posture; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D013995:Time; D055815:Young Adult