Hormonal contraceptives potentially reduce risk of tear to anterior cruciate ligament

Women on the combined pill appear to be less likely to tear a key ligament in their knee, research suggests.

Injuries to the anterior cruciate ligament in the knee are common, particularly in people taking part in sport, where such injuries sometimes end careers.

In November, the England footballer Jordan Nobbs ruptured her ACL, ruling her out of this year’s World Cup.

Tears to the ACL are known to be more common in women than men, with previous research suggesting fluctuations in hormones during the menstrual cycle, including oestrogen, might play a role by increasing the looseness of the ACL and making it more injury prone.

But some research has suggested hormonal contraceptives might mitigate such an effect – and now researchers say they have added to that evidence.

“[Oral contraceptive] use could be a potential way to modify the increased risk that changes in oestrogen can have on ACL tears,” said Dr Steven DeFroda, the first author of the study from Brown University in the US, adding that the researchers are looking to see how the “protective effect” changes if different levels or combinations of hormones are used.

Writing in the journal the Physician and Sportsmedicine , DeFroda and colleagues report that they looked at US insurance claims data between 2007 and 2017 for women aged 15 to 49.

From this, they were able to compare rates of ACL injury among those with a recent prescription for the combined pill – which contains synthetic versions of the hormones oestrogen and progesterone– with individuals similar in age, body mass index and general health but who did not have such a prescription.

The team found reconstruction surgeries to the ACL were more common in those without a prescription for the pill, at 569 reconstructions out of 82,874 women, compared with 465 operations among 82,874 women with such a prescription. When the team looked closer, they found this was primarily driven by differences in injury rates among women aged 15 to 19.

The researchers said that, among other reasons, this might be because women in this age group might be more likely to do more sport or intense physical activity than older women, while a smaller proportion of young women were typically on the pill, potentially increasing their risk of injury compared with older women. As a result, any differences between those on the pill or not might be more apparent in younger women.

While not recommending that female athletes start taking the pill to protect against knee injuries, DeFroda said they might want to discuss such benefits when choosing a contraceptive.

“Consideration should be given to prescribing [the pill] to younger athletes, after careful assessment of the risks of these commonly prescribed medications,” the authors wrote.

The study had limitations, however, including that it was not clear whether those with a prescription for the pill were taking it when they were injured. It was also unclear whether women with prescriptions had the same level of activity as those without, and the study did not look at ACL injuries that did not require surgery.

Jim Thornton, a professor of obstetrics and gynaecology at the University of Nottingham, said it was too soon to recommend women go on the pill to reduce injury risk, noting there were other factors that might explain why those not on the pill had higher ACL injury rates. He said some women might not take the pill because of a loss of menstruation resulting from high levels of exercise – which in itself could increase their chance of injury.

Nicola Maffulli, a consultant trauma and orthopaedic surgeon and professor of sport and exercise medicine at Queen Mary University of London, said hormonal variations could play a role in the rate of knee injuries in women – and the pill could reduce such variations.

But he also urged caution against women taking the pill to reduce the risk of a knee injury, pointing out any medication can bring negative side-effects.

“Neuromuscular or proprioception training is inexpensive, and sport-specific, and very effective in preventing anterior cruciate ligament injuries in women: it should be the first port of call in women who undertake sport, and wish to decrease their risk of ACL injuries,” he said. “They should not be recommended to start taking the pill to decrease their chances to tear their ACL.”