Abstract

Context: Of the individuals able to return to sport participation after an anterior cruciate ligament (ACL) injury, up to 25% will experience a second ACL injury. This population may be more sensitive to hormonal fluctuations, which may explain this high rate of second injury. Objective: To examine changes in 3-dimensional hip and knee kinematics and kinetics during a jump landing and to examine knee laxity across the menstrual cycle in women with histories of unilateral noncontact ACL injury. Design: Controlled laboratory study. Setting: Laboratory. Patients or Other Participants: A total of 20 women (age = 19.6 ± 1.3 years, height = 168.6 ± 5.3 cm, mass = 66.2 ± 9.1 kg) with unilateral, noncontact ACL injuries. Intervention(s): Participants completed a jump-landing task and knee-laxity assessment 3 to 5 days after the onset of menses and within 3 days of a positive ovulation test. Main Outcome Measure(s): Kinematics in the uninjured limb at initial contact with the ground during a jump landing, peak kinematics and kinetics during the loading phase of landing, anterior knee laxity via the KT-1000, peak vertical ground reaction force, and blood hormone concentrations (estradiol-β-17, progesterone, free testosterone). Results: At ovulation, estradiol-β-17 (t = −2.9, P = .009), progesterone (t = −3.4, P = .003), and anterior knee laxity (t = −2.3, P = .03) increased, and participants presented with greater knee-valgus moment (Z = −2.6, P = .01) and femoral internal rotation (t = −2.1, P = .047). However, during the menses test session, participants landed harder (greater peak vertical ground reaction force; t = 2.2, P = .04), with the tibia internally rotated at initial contact (t = 2.8, P = .01) and greater hip internal-rotation moment (Z = −2.4, P = .02). No other changes were observed across the menstrual cycle. Conclusions: Knee and hip mechanics in both phases of the menstrual cycle represented a greater potential risk of ACL loading. Observed changes in landing mechanics may explain why the risk of second ACL injury is elevated in this population. Verf.-Referat