Hormonal Contraceptive Use and Musculoskeletal Injury Risk in Female Athletes: A Prospective Cohort Study

Background: Female reproductive hormones are attributed to the higher rate of musculoskeletal (MSK) injuries among female athletes compared with male athletes. Purpose: To evaluate association between exposure to hormonal contraceptives (HCs), joint laxity, and number of injuries in female athletes over a 1-year period. Study Design: Cohort study. Level of Evidence: Level 3. Methods: Professional and Division I collegiate female athletes were recruited into 2 groups based on HC status (HC vs non-HC). Serum relaxin, estrogen and progesterone levels, knee laxity, generalized hypermobility, and lower extremity kinematics during a single-legged jump were examined during preseason in the luteal phase of each athlete’s menstrual cycle. Injuries were tracked for 1 year after testing. Results: Circulating levels of progesterone (non-HC, 38.9 ± 15.0 pg/mg vs HC, 28.6 ± 11.4 pg/mg; P < 0.01), estrogen (non-HC, 2.80 ± 3.0 pg/mg vs HC, 2.0 ± 3.0 pg/mg; P = 0.01), and relaxin (non-HC, 0.26 ± 0.08 pg/mg vs HC, 0.22 ± 0.03 pg/mg; P = 0.04) were lower in HC (n = 32) than in non-HC (n = 40) athletes during the luteal phase of the cycle. Non-HC athletes demonstrated significantly greater hip flexion at initial contact (non-HC, 29.42°± 7.64° vs HC, 25.25°± 7.13°; P = 0.02), and greater knee adduction (valgus) at maximum knee flexion (non-HC, –1.90°± 3.25° vs HC, –0.25° ± 3.40°; P = 0.02) during a single-legged drop. Average (±SD) injury count for non-HC athletes was 0.71 (±1.3) compared with 0.35 (±0.70) in the HC group ( P = 0.25). Injury count was correlated significantly to circulating levels of relaxin ( r = 0.32; P < 0.01). Conclusion: A potential relationship between increased circulating relaxin levels and the risk of injury was established. Athletes taking HCs demonstrated significantly reduced peak knee adduction angles when landing from a jump. Clinical Relevance: The results advance knowledge of relationships between specific hormones and injury risk, and the potential role of HCs on kinematic patterns when landing from a jump. Future research will determine HC formulations that may protect against MSK injury, and inform broader strategies to reduce sport-related injury risk in female athletes.