title: Lack of hormonal influences on mechanical properties of sheep knee ligaments.
abstract: BACKGROUND
  The number of anterior cruciate ligament injuries in female athletes exceeds that in male athletes at similar competitive levels. This difference has been attributed by some authors to hormone-mediated alteration in knee laxity in women.
  
  
  OBJECTIVE
  Sheep anterior cruciate and medial collateral ligament strength and stiffness are not altered by administration for 6 months of estrogen or a selective estrogen receptor agonist (raloxifene).
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Thirty-eight mature ewes were divided into five groups: sham operation (N = 6), ovariectomy (N = 9), ovariectomy and estradiol implant (N = 7), low-dose raloxifene (N = 9), and high-dose raloxifene (N = 7). After 6 months, the animals were sacrificed and ligaments were tested along with those from five rams' knees.
  
  
  RESULTS
  No differences were found between treatment groups for maximum force, stiffness, energy to failure, or failure site. The ultimate stress of the rams' anterior cruciate ligaments was significantly higher than that of the ewes.
  
  
  CONCLUSIONS
  Estrogen and estrogen receptor agonists at physiologic levels do not lead to decreased knee ligament strength.
  
  
  CONCLUSIONS
  The female hormonal milieu may not be responsible for the increased incidence of anterior cruciate ligament injury in female athletes compared with their male counterparts.
authors.affiliation: Hospital for Special Surgery, New York, New York 10021, USA.
authors.forename: Sabrina M
authors.initials: SM
authors.lastname: Strickland
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Belknap
authors.forename: Simon A
authors.initials: SA
authors.lastname: Turner
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Wright
authors.forename: Jo A
authors.initials: JA
authors.lastname: Hannafin
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000187:drug effects* / Q000502:physiology; D001696:Biomechanical Phenomena; D004305:Dose-Response Relationship, Drug; D004343:Drug Implants; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D017888:Medial Collateral Ligament, Knee / Q000187:drug effects* / Q000502:physiology; D010052:Ovariectomy; D020849:Raloxifene Hydrochloride / Q000494:pharmacology*; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D012756:Sheep; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000187:drug effects; D013997:Time Factors
chemical_list: D004343:Drug Implants; D020845:Selective Estrogen Receptor Modulators; D020849:Raloxifene Hydrochloride; D004958:Estradiol