Oral contraceptive use, or birth control pill, is associated with an approximately 18-20% reduction in the risk of ACL injuries requiring surgery, though the evidence is mixed and the protective effect may vary by age. A recent study notes that hormonal contraceptives provide protection regardless of delivery method (oral, device, or systemic), though this effect is not consistently seen in females aged 15-19 years.
Epidemiological Evidence
The largest study from the Danish Knee Ligament Reconstruction Registry analyzed 4,497 women with operatively treated ACL injuries and 8,858 matched controls. The adjusted relative risk for ACL injury was 0.82 comparing oral contraceptive users to non-users-that is, those using oral contraceptive bills seemed to have less ACL tears. A US insurance claims study of women ages 15-35 found that systemic hormonal contraceptive use was associated with lower incidence of ACL surgery. However, when broken down into age groups, female patients 15 to 19 years showed no difference.
A 2024 database study examining musculotendinous injuries found that females taking oral contraceptives had significantly lower rates of lower-extremity skeletal musculotendinous injuries compared to non-oral contraceptive females and males.
Mechanistic Evidence
Animal studies provide biological plausibility for the protective effect. Oral contraceptive formulations with higher progestin-to-estrogen ratios significantly increased ACL strength in rats, with the order from strongest to weakest ACLs matching the highest to lowest progestin-to-estrogen ratios. The proposed mechanism involves counteracting the effects of relaxin, which increases ligament laxity and may predispose to injury.
Conflicting Evidence and Limitations
A 2023 systematic review of 50 studies examining combined hormonal contraceptives and musculoskeletal outcomes concluded there is insufficient high-certainty evidence that oral contraceptives are protective against musculoskeletal injuries. Biomechanical studies have not consistently demonstrated differences in ground reaction forces or knee valgus forces between oral contraceptive users and non-users.
The menstrual cycle itself appears to influence ACL injury risk, with most studies showing increased injuries during the preovulatory or ovulatory phases when estrogen peaks. A 2025 prospective cohort study found the highest injury incidence during the estimated ovulatory phase compared to follicular and luteal phases. Oral contraceptives may reduce injury risk by stabilizing hormonal fluctuations and preventing the estrogen surge associated with ovulation.
Clinical Implications
While the epidemiological data suggest a modest protective association, oral contraceptives should not be prescribed solely for ACL injury prevention given the mixed evidence, potential side effects, and lack of prospective randomized trials. The protective effect appears most consistent in women over age 20, with unclear or paradoxical findings in adolescents.
Formulations with higher progestin-to-estrogen ratios may offer greater protection based on preclinical data, though this requires clinical validation.
Amit Momaya, MD is a board certified orthopedic surgeon who specializes in sports medicine. He serves as the Chief of Sports Medicine at UAB, resides on the editorial board of research journals, and takes care of several collegiate and professional teams in Alabama. This blog post is for educational purposes only. Please consult with your physician for a discussion on oral contraceptive use and ACL injury risk.
