Sex Differences in Knee Joint Laxity Change Across the Female Menstrual Cycle

Abstract

Sex differences in knee laxity were menstrual cycle dependent, coinciding with significant elevations in estradiol levels. Females had greater laxity than males on day 5 of menses, days 3-5 near ovulation, days 1-4 of the early luteal phase and days 1, 2, 4 and 5 of the late luteal phases. Within females, knee laxity was greater on day 5 near ovulation compared to day 3 of menses, and days 1-3 of the early luteal phase compared to all days of menses and day 1 near ovulation. On average, differences observed between sexes were greater than those within females across their cycle. There were no differences in anterior knee stiffness between sexes or within females across days of the menstrual cycle.