Hormonal changes throughout the menstrual cycle and increased anterior cruciate ligament laxity in females

To determine whether women experience significantly greater anterior cruciate ligament (ACL) laxity in conjunction with estrogen and progesterone surges during a normal 28- to 30-day menstrual cycle.

Serial estrogen and progesterone levels were measured via radioimmunoassay procedures to identify the follicular and luteal phases of a subject's menstrual cycle and to determine periods of peak hormonal surges. Concomitant ACL laxity measures were taken using a knee arthrometer. Hormone levels and ACL laxity were assessed on days 1, 10, 11, 12, 13, 20, 21, 22, and 23 of the menstrual cycle. Day 1 corresponds to the menstrual phase, when estrogen and progesterone levels are at their lowest. Days 10 through 13 correspond to peak estrogen surge (follicular phase), and days 20 through 23 correspond to peak progesterone surge (luteal phase).

Seven active females between the ages of 21 and 32 years with at least one apparently healthy knee (no known knee anomalies) volunteered for participation in this study. Each subject stated that she experienced a normal (28- to 30-day) menstrual cycle and was not currently taking any type of hormone therapy (eg, birth control medication).

Blood was drawn on days 1, 10, 11, 12, 13, 20, 21, 22, and 23 of each subject's menstrual cycle, and ACL laxity measurements were assessed immediately after the blood draws. Estrogen and progesterone levels were determined via radioimmunoassay procedures, and ACL laxity was determined using a knee arthrometer.

A within-subjects, repeated-measures analysis of variance was applied to determine the presence or absence of significant differences in ACL laxity values over the course of a subject's menstrual cycle. We found a significant difference in ACL laxity when comparing baseline levels of estrogen with peak levels of estrogen. A significant increase in ACL laxity was also noted when comparing baseline levels of progesterone with peak levels of progesterone.

ACL laxity increased significantly throughout the menstrual cycle when comparing baseline with peak levels of estrogen and progesterone.