An ACL injury can be one of the most catastrophic injury that can occur in sports. It often requires a long lay off, months of rehab, and expensive surgery.
Before we can talk about how to prevent an ACL injury, we need to find out HOW it happens.
Lets look at the risk factors first. What attributes make you more likely to rupture your ACL?
Female- Females are more likely to rupture their ACL (some studies show they are 3 x more likely). This has been seen on the AFLW, with a huge amount of female athletes rupturing their ACL. There are a number of reasons for that, including the difference in muscle control and strength, and the larger Q- angle (angle lining up the femur and the knee)
Sports involving pivoting or sudden deceleration- we will go through the exact mechanism later on, but sports like soccer, rugby, skiing, or volleyball that require change of direction or sudden deceleration are a risk factor for ACL injury
Previously torn ACL- it sounds silly, but a major risk factor for an ACL injury…is a previous ACL injury
Fitness– When you are fit, you tend to move better, whereas when you are fatigued, you are going to move poorly and sloppily. ACL injuries often occur towards the end of the game, so being able to maintain your fitness for the whole game will help reduce injury. (This goes for all injuries to be honest)
So how does an ACL injury occur?
There are two main ways an ACL injury can occur- either jumping and landing poorly, or during the act of change of direction
. There are a number of factors that occur for a ACL to rupture.
Deceleration– Change of direction requires effective deceleration, before accelerating in a different direction. Not being able to decelerate effectively is a major risk factor for ACL rupture
Hip position– The hip will normally be abducted (move away from the body). This is a key component of an ACL injury, often your leg will be outside your centre of mass. The above picture illustrates this well. The foot and knee are well away from where the hip is, while the player is change direction.
Knee position– This is an easy one, and the most commonly described. “knee valgus” is the term used to describe the position of the knee. This is when the knee ‘buckles in’. The below picture illustrates this well. Secondly, the knee will frequently be in a position of extension.
Furthermore, during an ACL rupture, there will often be a twisting motion at the knee joint, further stressing the ACL.
Foot and ankle position- This one is more subtle, and arguable the least important mechanism in an ACL injury. The foot will often pronate (or collapse in) during an ACL injury. That is not to say that if you have flat feet you are more likely to get an ACL injury.
The ankle is another interesting one. Studies have shown that the more you can dorsiflex (move your foot up towards you), the more likely you are to get an injured ACL. This is most likely because people who have greater range of motion, tend to have more lax ligaments, and therefore are a bigger injury risk, rather than meaning that you should try and get a stiff ankle.
So there you have it. A brief look at how an ACL injury occurs. Next time, we will look at what you can do to prevent an ACL injury from occuring!