Birth Control Pills Decrease Likelihood of Knee Injuries

Young women who take birth control pills are less likely to have serious knee injuries, says new research from The University of Texas Medical Branch at Galveston. The study is published in Medicine & Science in Sports & Exercise.

As indicated in the March 18, 2016 news release, “Using a national insurance claims and prescription database of 23, 428 young women between 15 and 19, the study found that women with an ACL [anterior cruciate ligament] knee injury who were taking the birth control pill were less likely to need corrective surgery than women of the same age with ACL injuries who do not use the birth control pill. Researchers have proposed that the female hormone estrogen makes women more vulnerable to ACL injury by weakening this ligament. A previous investigation found that more ACL injuries in women occur during the points of their menstrual cycle when estrogen levels are high.”

“Birth control pills help maintain lower and more consistent levels of estrogen, which may prevent periodic ACL weakness, ” said lead author and M.D., Ph.D. student Aaron Gray. “With this in mind, we examined whether oral contraceptive use protected against ACL injuries that require surgery in women.”

Women between15-19 years old in need of ACL reconstructive surgery, the age group with the highest rates of ACL injuries by a wide margin, were 22% less likely to be using the birth control pill than non-injured women of the same age.

Gray told OTW, “I had previously been working on a biomechanics investigation to determine whether specific athletic maneuvers might predispose women to ACL injury more so than men. During this study, my literature search revealed that a large portion of the excessive ACL injuries in women might be occurring due to the presence of estrogen. Many previous studies have shown that the ACL is weaker during the first two weeks of the menstrual cycle when estrogen is present. It is also known that oral contraceptives, as a consequence, reduce estrogen levels or help to maintain a constant level of estrogen. It was biologically plausible that their use could potentially prevent these injuries. Two previous studies attempted similar investigations to this one, but the numbers were just not there to draw any meaningful conclusions. We then performed a pilot, using a small subset of the Clinformatics Data Mart claims data and fewer covariates, and found encouraging results to begin planning and performing this much broader study.”

“Orthopedic surgeons should, foremost, be aware that estrogen does play a role in ACL injury. It appears that the use of birth control pills mitigates some of this risk, especially during the late teenage years. Teenage girls involved in competitive sports should be provided information on injury prevention including proper conditioning, recovery from injury, and medication use, including the potential athletic benefits of birth control use. The present research does not make any comment on injury risk post-reconstruction. How a reconstructed ACL will respond to oral contraceptive use is still unknown.”