Conclusion : The literature suggests an association between hormonal fluctuations and ACL injury .
Recent studies have suggested that oral contraceptives may offer up to a 20 % reduction in risk of injury .
Background : Women are at substantially greater risk for anterior cruciate ligament ( ACL ) injuries than are men .
Purpose : To conduct a systematic review and meta- analysis of the literature to clarify the effect of the menstrual cycle and contraceptives on the laxity of and noncontact injuries to the ACL .
Knee ligament behavior following a controlled loading protocol does not differ by menstrual cycle day.
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 . FINDINGS 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 . INTERPRETATION Following a controlled , static external load , displacement and stiffness were not affected differently by day of the menstrual cycle
Conclusion : The literature suggests an association between hormonal fluctuations and ACL injury .
Recent studies have suggested that oral contraceptives may offer up to a 20 % reduction in risk of injury .
Background : Women are at substantially greater risk for anterior cruciate ligament ( ACL ) injuries than are men .
Purpose : To conduct a systematic review and meta- analysis of the literature to clarify the effect of the menstrual cycle and contraceptives on the laxity of and noncontact injuries to the ACL .