Why are women more susceptible to ACL tears?

It’s a conundrum which has bothered sports experts for years, and it’s borne out by statistical weight: women are two to four times more likely than men to tear the anterior cruciate ligament. But why? A recent study conducted by Duke University in Durham, North Carolina endeavoured to solve the mystery, and their findings make interest reading.

According to previous research, the reason why women are more susceptible to ACL tears pointed to an assumption that it was because their knees move differently – but the team at Duke weren’t so sure. So, they deployed a forensic approach to reconstruct injuries by examining bone bruises on the knees of 15 men and 15 women with torn ACLs.

While other studies have deployed patient interviews and slow-motion replays, the Duke team realised that video footage was ineffective in determining the precise position of the knee and the time of injury through footage. Instead, they used MRI scans taken within a month of the ACL rupture, identified bruises on the surface of the two large bones that collide when the ACL tears – the femur and the tibia – and then used 3D modelling and computer algorithms to reconstruct the position of the knee when the injury occurred. Their findings? Males and females actually have the same position of injury.

The team at Duke have been using their advanced imaging and modelling technology to great effect over the past decade in the field of ACL research, including debunking the notion that an inward buckling of the knee was the cause of an ACL tear, discovering that landing on an extended knee was the prime culprit. So, when they make a statement, the sports medicine world takes notice.

However, this current report still leaves us in the dark as to why women are more susceptible to ACL tears than men. Here’s what we know so far:

• Women tend to have a narrower intercondylar notch – the groove in the femur through which the ACL travels – and a smaller ACL, which makes them more prone to injury.
• Women typically have a wider pelvis, which makes the thigh bones angle downward more sharply than in men, which leads to more pressure applied to the inside of the knee, which can cause the ACL to tear.
• Women’s ligaments tend to have more laxity, or ‘give’, than men’s, leading some experts to conclude that the excessive joint motion could be a factor in a higher ACL tear rate.
• Research shows that the muscles stabilising the knee may take a millisecond longer to respond in women than in men, leading experts to speculate that this minuscule difference in contraction time could lead to a higher rate of injury.
• Female athletes typically have weaker hamstring strength when compared to male athletes, leading to the hamstring having difficulty in balancing the power of the quadriceps, which in turn can lead to injury.

As with all athletes, regardless of sexual orientation, conditioning, strength training and proper coaching are your best defence against an ACL tear. Therefore, if you feel your training programme is lacking any of those factors, it’s time for a rethink.