title: The effects of estrogen on material and mechanical properties of the intra- and extra-articular knee structures.
abstract: BACKGROUND
  Female athletes have a higher incidence of anterior cruciate ligament injuries than do male athletes in similar sports. Hormones, particularly estrogen, have been indicated by some studies to be correlated with the disproportionate number of anterior cruciate ligament injuries in female athletes.
  
  
  OBJECTIVE
  Estrogen does not affect the mechanical or material properties of primate anterior cruciate ligaments or patellar tendons.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Twenty-six cynomolgus monkeys (Macaca fascicularis) were divided into 2 groups: sham operated (estrogen maintained, n = 12) and ovariectomized (estrogen deficient, n = 14). After 2 years, the animals were sacrificed, and various properties of ligaments were tested. Two different ligaments were studied, the anterior cruciate ligament and patellar tendon.
  
  
  RESULTS
  No differences were found between the sham-operated (sham) and ovariectomized group for failure load (anterior cruciate ligament: sham, 394 +/- 67 N; ovariectomized, 392 +/- 96 N; P > .74), stiffness, elongation at failure, ultimate stress (anterior cruciate ligament: sham, 115 +/- 30 MPa; ovariectomized, 128 +/- 36 MPa; P > .58), ultimate strain, modulus, failure sites, or energy to failure.
  
  
  CONCLUSIONS
  Endogenous estrogen does not directly affect the mechanical or material properties of the anterior cruciate ligament or the patellar tendon of cynomolgus macaques.
  
  
  CONCLUSIONS
  This study supports the idea that knee ligament injury in female athletes is not a direct result of estrogen's effect on ligament properties.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Ave, Ste R200, Minneapolis, MN 55454, USA.
authors.forename: Fred A
authors.initials: FA
authors.lastname: Wentorf
authors.forename: Kenji
authors.initials: K
authors.lastname: Sudoh
authors.forename: Christina
authors.initials: C
authors.lastname: Moses
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Arendt
authors.forename: Cathy S
authors.initials: CS
authors.lastname: Carlson
mesh_terms: D000818:Animals; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D004967:Estrogens / Q000097:blood / Q000502:physiology*; D005260:Female; D007718:Knee Injuries / Q000453:epidemiology / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000503:physiopathology*; D008252:Macaca fascicularis; D012737:Sex Factors
chemical_list: D004967:Estrogens