The “X’s and Y’s” of ACL Tears

August 15, 2017

The Dreaded Season Ending ACL Injury

With soccer season in full swing this fall, don’t be surprised if you hear the news highlight of athletes getting hurt, specifically tearing their anterior cruciate ligament, or ACL. Although the ACL is the most common knee ligament injury, it can also be accompanied by tears of the medial collateral ligament (MCL) and medial meniscus. This combination has been coined the “unhappy triad” or “terrible triad” and is the most common multi-ligament injury. What you might not realize is that females are more susceptible to such injuries than males.

Why a higher risk for females? Although many studies and research trials have clearly identified that females are currently at a higher risk for tearing their ACL’s, it is much more difficult to determine what the exact cause for this may be. Some research suggests that hormonal changes associated with the menstrual cycle may adversely affect the ACL. In addition, there are several anatomic differences between the genders that may contribute to injury risk.

First, a larger “Q-angle” puts females at greater risk. The Q-angle is measured by the angle formed between the quadriceps (thigh) muscle and patella (kneecap) tendon. Anatomically, a woman’s pelvis is wider for child-bearing purposes. If a valgus deformity (a knock-kneed position) is present, that can place more stress on the knee joint. Second, the shape of the notch in the knee joint where the ACL attaches may predispose females to these tears. The notch can be either U- or V-shaped, and one surgeon noted seeing more ACL tears in V-shaped notches.

While these anatomic/physiologic factors may increase females’ risk for ACL tears, what do you do with this information since there isn’t anything you can do about them? Fortunately, these aren’t the only things associated with risk for ACL tears. There is no proven formula for preventing the tears but understanding and addressing the biomechanical factors of the knee has been shown to reduce the risk (see “The ‘X’s and O’s’ of ACL Tears” in this issue) regardless of gender.



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