title: Knee ligament behavior following a controlled loading protocol does not differ by menstrual cycle day.
abstract: BACKGROUND
  Females experience a disproportionate number of anterior cruciate ligament injuries compared to males. Increased estradiol concentration has been suggested to alter ligament properties and strength. Determining whether the knee responds differently to an external load at various hormonal levels may be helpful in further explaining the gender disparity.
  
  
  METHODS
  Estradiol, progesterone and testosterone were quantified at menses, near ovulation and at the mid-luteal phase. With one knee serving as the control limb and the other as the experimental limb, displacement at 134N and stiffness between 90 and 134N were recorded with a knee ligament arthrometer on both knees before and after a loading protocol. The protocol consisted of three, 3-min, posterior to anterior normalized loads directed to the posterior calf with a ligament testing device.
  
  
  RESULTS
  The loading protocol produced a measurable increase in displacement but not stiffness. Neither displacement nor stiffness measures however were affected by day of the menstrual cycle. No consistent relationships between hormonal concentrations and displacement or stiffness were evident.
  
  
  CONCLUSIONS
  Following a controlled, static external load, displacement and stiffness were not affected differently by day of the menstrual cycle.
authors.affiliation: Department of Physical Therapy, Rangos School of Health Sciences, Duquesne University, Pittsburgh, PA 15282, USA. carcia@duq.edu
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Carcia
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shultz
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Granata
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Gansneder
authors.forename: David H
authors.initials: DH
authors.lastname: Perrin
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology*; D004548:Elasticity; D004958:Estradiol / Q000097:blood; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008597:Menstrual Cycle / Q000502:physiology*; D010808:Physical Examination / Q000379:methods; D010812:Physical Stimulation / Q000379:methods*; D011374:Progesterone / Q000097:blood; D013739:Testosterone / Q000097:blood; D016474:Weight-Bearing / Q000502:physiology*
chemical_list: D012739:Gonadal Steroid Hormones; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol