Abstract

Objective: An increase in knee laxity during the menstrual cycle may increase the risk of ACL injury. The objective of this study was to investigate whether changing knee laxity during the menstrual cycle is correlated with changing knee joint loads in a cutting maneuver.

Design: Cross sectional study.

Setting: Laboratory testing

Participants: Twenty-five healthy females, with a normal menstrual cycle, no history of oral contraceptive use and no previous knee injury.

Interventions: Serum hormone levels were assessed and knee joint laxity at a load of 89N was measured during the follicular, ovulation and luteal phases. Participants performed 10 trials of a cutting maneuver to quantify knee joint mechanics at each test session.

Main outcome measurements: Knee joint laxity (mm), peak knee angle (°) and knee joint moment (Nm) and knee joint impulse (Nms).

Results: Increased knee laxity was observed during ovulation compared to the luteal phase while no significant changes in knee mechanics corresponding to menstrual phases were found. A positive correlation was found between changes in knee laxity (Δlaxity) and changes in knee joint loads (Δmoment or Δimpulse) from the follicular phase to ovulation, and from ovulation to the luteal phase (P<0.05). Females who increased knee laxity showed increased knee loads while others who decreased knee laxity showed decreased knee loads during the menstrual cycle.

Conclusion: Knee laxity is positively correlated with knee joint loads, and increased knee laxity during the menstrual cycle may be a potential risk factor for ACL injuries in specific females during sports activity.