Bad news, ladies: Women who participate in jumping and pivoting sports are four to six times more likely to tear their ACLs than men in the same sports, according to a 2010 study published in the North American Journal of Sports Physical Therapy. The worst part, however, is that there's not a ton we can do about it.
Naturally, we wanted to know all the details, so we chatted with Armin Tehrany, M.D., an orthopedic surgeon and shoulder and knee specialist and founder of Manhattan Orthopedic Care. He told us exactly why women are at a higher risk for tearing their anterior cruciate ligament (ACL) and how to keep it right where it's supposed to be.
Your hips don't lie; they can have a serious effect on your risk of tearing an ACL. But what do curves have to do with it?
First things first: The ACL is a ligament running through the middle of your knee, and its main job is to provide rotational and overall stability by limiting the amount of movement between the tibia and femur.
Women are more likely to have issues with this ligament because the wider a person's pelvis is, the greater the angle between the femur (the thigh bone) and the tibia (the shin bone), says Tehrany.
"The alignment of a man's leg is straight because they have a narrower pelvis," says Tehrany. "A woman has a wider pelvis, so the knee is no longer aligned straight. It's more at an angle, which means the ACL is at more risk for a twisting injury." And it's not an equal risk for all women; those with wider hips (note: we're talking about the width of your actual pelvis bone, not your fleshy curves) have a higher risk than a woman with narrower hips.
There's also the issue of the notch in the femur bone around the ACL. It's usually smaller in women, which also has been linked to a higher risk of tearing. Sadly, both are anatomical things that we can't do a damn thing about. (Check your form during your workout. These exercises might just cause a knee injury too.)
Your Menstrual Cycle
You can blame your cycle for mood swings, cramps, cravings... And now, you can blame it for an increased risk for ACL injury. (Ugh, this isn't the only way your cycle can impact your workout.)
"When there are hormonal changes during the menstrual cycle, women's ligaments and joints can get looser," says Tehrany. "Women usually have looser joints and ligaments than men to begin with, and then the menstrual cycle can make them get even looser, which means that during pivoting sports or shifting of the knee, the ACL is under more risk of tearing."
But unlike some of the other lovely gifts women get just before their periods, the risk for ACL tear is at a different time of the month. (Seriously, are we ever gonna catch a break?) Women were shown to have a higher risk for ACL tear during their pre-ovulatory phase of their menstrual cycle (the section of their cycle before ovulation) than the post-ovulatory phase of their cycle (the section of their cycle between ovulation and the next period), according to a study published in the Journal of Athletic Training. Tehrany recommends that patients wear a knee brace (a hinged sleeve that you can get at a drugstore) if they're feeling particularly "loose-jointed" at any point in their cycle.
An interesting related fact: Teenage girls age 15 to 19 taking oral birth control pills—which lessen and stabilize estrogen levels—had a slightly lower risk for ACL tear than the general population, according to a study in Medicine & Science in Sports & Exercise. But while there might be a slight connection between birth control and a decrease in ACL tear risk, you shouldn't try to get on the Pill simply to protect your knees, says Tehrany.
Your Quad-Hamstring Balance
Time for the good news! There's a risk factor you can control: the balance in strength between your quadriceps and your hamstrings.
"A lot of times a woman's hamstrings are not as strong as the quadriceps," Tehrany says, but it's hard to determine whether you have an imbalance on your own. "Women should seek out a professional—either a physical therapist or personal trainer—for advice on whether or not they have stability between the quad muscles in the front of the knee, versus the hamstring muscles on the back of the knee."
Even if you're not positive about your quad-hamstring balance, it can't hurt to make sure you're doing some overall lower-body strength training on the reg. Strengthening these two big muscle groups, in general, will help stabilize the knee, says Tehrany. (Try these trainer-approved moves for stronger hamstrings or this leg workout for knee pain.)
Another way to stabilize: plyometric workouts. If you play a sport that requires a lot of pivoting and turning, or if you're just trying to protect your knees during boot camp suicide sprints, adding plyometrics that help you prep for those movements has been shown to decrease the likelihood of ACL tear, says Tehrany. For high school female athletes, performing a pre-season program of flexibility, plyometric, strength, and landing-pattern training significantly decreased their risk of knee injury, according to one study published in the American Journal of Sports Medicine. (Just what the doctor ordered; here's a lower-body plyo workout you can try.)
ACL injury isn't inevitable. You're better off if you train well for your sport or workout, and play it smart with what you're doing with your body. After all, as Tehrany says, "The easiest way to treat an ACL injury is to prevent one."