title: Sagittal alignment of the knee and its relationship to noncontact anterior cruciate ligament injuries.
abstract: BACKGROUND
  Knee hyperextension and tibial posterior slope are related to sagittal alignment of the knee. The relationship of sagittal alignment to noncontact anterior cruciate ligament (ACL) injuries has been reported with conflicting results.
  
  
  OBJECTIVE
  To determine whether there is a difference in sagittal alignment of the knee between an ACL-deficient group and a negative control group and to find risk factors contributing to noncontact ACL injuries.
  
  
  METHODS
  Cross-sectional study; Level of evidence, 3.
  
  
  METHODS
  Magnetic resonance images of the knee in full extension were acquired in the patient group, which consisted of 33 male and 40 female patients with noncontact ACL injuries, and in the negative control group, which consisted of 28 male and 30 female participants. Three angles were measured: the angle between the femoral axis and the tibial axis, designated as the extension angle; the femoral plateau angle, between the femoral axis and a line tangent to the concave profile of the medial tibial plateau (P line); and the tibial posterior slope angle, 90° minus the angle made by the intersection of the tibial axis and the P line.
  
  
  RESULTS
  In the female group, the femoral plateau angle and the tibial posterior slope angle were significantly larger in the ACL-deficient patients than in the negative control group, although these differences were not seen in the male group. In the female subjects, a negative correlation between the extension angle and the tibial posterior slope angle was seen in the ACL-deficient group, suggesting that knees with hyperextension had a small tibial posterior slope, whereas knees without hyperextension had a large tibial posterior slope.
  
  
  CONCLUSIONS
  There were 2 types of large femoral plateau angles: one had its origin in an increasing tibial posterior slope; the other resulted from hyperextension of the knee. Large posterior tibial slope and hyperextension are both correlated with noncontact ACL injury in women.
authors.affiliation: Social Insurance Gunma Central General Hospital, Gunma, Japan. mterauchi@mac.com
authors.forename: Masanori
authors.initials: M
authors.lastname: Terauchi
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Hatayama
authors.forename: Sinya
authors.initials: S
authors.lastname: Yanagisawa
authors.forename: Kenichi
authors.initials: K
authors.lastname: Saito
authors.forename: Kenji
authors.initials: K
authors.lastname: Takagishi
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000209:etiology*; D007719:Knee Joint / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D012307:Risk Factors; D012727:Sex Characteristics; D055815:Young Adult