title: Intrinsic Predictive Factors of Noncontact Lateral Ankle Sprain in Collegiate Athletes: A Case-Control Study.
abstract: BACKGROUND
  Lateral ankle sprain (LAS) is one of the most common injuries in sports. Despite extensive research, intrinsic factors that predict initial and recurrent noncontact LAS remain undefined.
  
  
  OBJECTIVE
  To identify the predictive factors of initial and recurrent noncontact LAS, focusing on ankle flexibility and/or alignment in collegiate athletes.
  
  
  METHODS
  Case-control study; Level of evidence, 3.
  
  
  METHODS
  A total of 191 athletes were assessed during the preseason for factors predictive of noncontact LAS. The baseline measurements included weightbearing dorsiflexion range of motion (ROM), leg-heel angle, foot internal rotation angle in plantar flexion, classification according to the mortise test, and navicular-medial malleolus (NMM) distance. Occurrence of noncontact LAS and participation in practice and games were prospectively recorded for 11 months.
  
  
  RESULTS
  Of the 191 athletes assessed, 169 (145 males, 24 females) completed the study; 125 athletes had a history of ankle sprain. During the observational period, 16 athletes suffered noncontact LAS (0.58 per 1000 athlete-exposures) consisting of 4 initial sprains and 12 recurrences. The hazard ratio estimated by a Cox regression analysis showed that athletes with an NMM distance ≥4.65 cm were 4.14 times more likely to suffer an initial noncontact LAS than were athletes with a shorter NMM distance (95% confidence interval, 1.12-14.30) and that athletes with a weightbearing dorsiflexion ROM >49.5° were 1.12 times as likely to suffer a recurrent noncontact LAS compared with athletes with a lower ROM (95% confidence interval, 1.05-1.20).
  
  
  CONCLUSIONS
  NMM distance predicts initial noncontact LAS, and weightbearing dorsiflexion ROM predicts recurrent noncontact LAS.
authors.affiliation: Graduate School of Medical Technology and Health Welfare Sciences, Hiroshima International University, Hiroshima, Japan. ; Department of Physical Therapy, Hokkaido Chitose Institute of Rehabilitation Technology, Hokkaido, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Department of Sport Education, School of Lifelong Sport, Hokusho University, Hokkaido, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Department of Sport Education, School of Lifelong Sport, Hokusho University, Hokkaido, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Graduate School of Medical Technology and Health Welfare Sciences, Hiroshima International University, Hiroshima, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Gamada
keywords: ankle dorsiflexion; collegiate athlete; navicular–medial malleolus distance; noncontact lateral ankle sprain