Oral contraceptives may lower the risk of serious knee injuries in women, according to a large-scale observational study. The study, published in The Physician and Sportsmedicine journal, involved over 165,000 female patients aged between 15 and 49.
Researchers from Brown University analysed a decade of prescription and insurance information from a large US national database.
They found that oral contraceptives were most protective in young women aged 15-19 years, who were 63 per cent less likely to need reconstructive surgery following anterior cruciate ligament (ACL)injury compared with aged matched controls.
The findings have important implications for the nearly one in two athletes with ACL tears who are unable to return to athletic competition, and the 20-50 per cent who develop arthritis within 10-20 years of their injury, researchers said.
ACL injuries are extremely common, especially among the young athletic population, and are two to eight times more common in women than men. Previous research suggests that elevated estrogen may play a role in female athletes' greater risk of ACL injury. The researchers analysed the records of female patients who were taking the most common types of oral contraception.
Rates of ACL reconstruction in women taking oral contraceptives during the 12 months prior to injury and undergoing surgery (82,874) were compared to a control group of the same age with a similar injury who were not taking oral contraceptives (82,874).
A total of 465 women in the oral contraceptive group required surgical reconstruction of the ACL between 2007 and 2017 compared to 569 in the control group. Results showed that women taking oral contraceptives were 18 per cent less likely to require reconstructive surgery compared to matched controls.
The researchers speculate that taking pills containing the hormones estrogen and progesterone may suppress the hormonal surges during the menstrual cycle, leading to a lower rate of injury. "It's likely that oral contraceptives help maintain lower and more consistent levels of estrogen and progesterone, which may lead to periodic increase in laxity and subsequent risk of tear," said Steven DeFroda from Brown University, who led the study.
While acknowledging the potential risks, the study authors conclude that the findings support the use of oral contraceptives in elite high school and college-aged athletes, especially those at higher risk of ACL tears such as soccer and basketball players. "Young athletes use oral contraceptives for a variety of reasons including regulating their menstrual cycle and/or preventing pregnancy. "With careful assessment of the risks, injury risk reduction could be another way in which female athletes may benefit from their use," said DeFroda.
This is an observational study, so no firm conclusions can be drawn about cause and effect.
The authors point to several limitations of the study, including that it only examined a limited number of risk factors such as age and comorbidity. It did not assess participation in sports/activity level that might explain why some women tore their ACLs and others did not.