ACL Injury
Why care?
Tearing of the infamous anterior cruciate ligament (ACL) is one of the most common and devastating injuries to loom over the sport of soccer. The injury has been cited as being at least 2-3 times (often cited even 4-6X) more common in females than males across sports (even higher in soccer) and the majority of these are non-contact in nature (often cited to be ~70%). For those who do suffer a complete tear, most have surgery to reconstruct their ACL and require 4-9 months, minimum, to return to playing afterwards. What’s more, asymmetrical movement patterns (compensations) and muscle activation have been repeatedly shown to be present up to and beyond 2 years after the original injury date. This and other factors are why there is a shockingly high rate of subsequent, second ACL tears after sustaining one (up to 30% of individuals). Additionally, young onset osteoarthritis has been observed at significantly higher rates in people following serious joint injuries, leading to pain and decreased function/performance. Needless to say, you do not want to tear your ACL. So, prevention is key.
How & Why:
The ACL primarily resists anterior translation of the tibia, and secondarily internal rotation of the tibia on the femur. In more straight forward terms, it helps prevent your shinbone from sliding forward or rotating inwards (counter-clockwise when you look down at it) relative to your thigh-bone. The most common mechanisms of non-contact ACL injury are poor biomechanics and lack of control during cutting, deceleration, and landing after a jump. The faulty, high-risk biomechanics are most simply explained as allowing the knee to ‘cave inwards’ during any of these aforementioned movements when the foot is planted. If you imagine a line between your ankle and hip (looking from the front or when facing a mirror), your knee should not fall inside (i.e. not towards your body’s midline) of this line. It should stay inline throughout the full range of motion or the whole movement, or even slightly outside of it. The more the knee ‘falls in’, the more aberrant and risky the mechanics become.
When you cut, your lower body goes through a controlled range of motion at the ankle, knee and hip simultaneously. These movements are controlled both actively (i.e. by muscles) and passively (i.e. by bones and ligaments). If the muscles are not strong enough to control the motion, or if they are not being activated in a good motor pattern (to promote natural alignment of bones & ligaments), then the passive structures will end up taking the load. This is what happens with non-contact ACL tears. The active structures don’t pull their weight, the passive structures are forced to pick up the slack, and the ACL is pushed beyond its limits, leading to its failure (tearing). Therefore, you must learn to use more active muscular control.
Prevent it:
Newly published, 2018 Clinical Practice Guidelines (the ‘take away’ from a massive review of available literature) found that knee injuries - including ACL - can be significantly prevented using player screening and targeted pre- and intra-season exercise programs.
In short, strengthen your hamstrings (particularly eccentrically), gluteus maximus, and gluteus medius. What are some of the best exercises for these? Romanian (straight-leg) deadlifts (hammies, glute max), eccentric hamstring ball rollouts (hammies, glute max), hip thrusters (glute max), lateral band walks (glute med and max), and oil drillers with resisted abduction (glute med and max – some hamstring). Furthermore, you need repetition with using a new, more controlled and safer movement pattern in order to train your body to automatically perform in this way during game-time situations. Single leg triple jumps (sticking the single-leg landing) with a mirror or video camera in front of you can help you to check your own form. Are you letting the knee “cave in”? Can you fix it? Try again. If you aren’t able to - maybe your need more strength of those muscles (listed above - specifically the glutes) first!
As a helping hand, a licensed physical therapist is someone who commonly rehabs individuals following ACL injury, and is capable of observing your movements, screening you for deficits, and helping you to correct them. When in doubt, this should be your go to.
If you would like to follow a specific program, an innumerous number exist. One of the most successful for overall knee injury prevention has been shown to be the program used by Knakontroll et al. For ACL injury, specifically, the Knakontroll, PEP (Prevent injury & Enhance Performance), and Caraffa et al programs have been shown to be most successful. For some of the most commonly employed exercises, see our training & performance exercise database.
Although the chance of tearing your ACL cannot be completely eliminated, you can significantly decrease your risk, without a doubt. As stated above, movements must be controlled by either passive or active structures. To protect the passive ACL structure, active musculature can be strengthened and trained to assist in sharing the load. Passively, the ACL resists anterior translation and internal rotation of the shin. Actively, the hamstrings resist anterior tibial translation, the gluteus maximus resists hip internal rotation (prevents knee from ‘falling in’), and the gluteus medius resists hip adduction (which puts the knee in vulnerable position, essentially ‘falling in’). Training your nervous system to activate these and other active muscles appropriately in order to control your athletic maneuvers with good control and alignment requires feedback of your performance (eg use of a mirror or camera), and tons of repetition.
Doing these things will substantially decrease your risk of spending your season on the sideline.
So don’t just train - train smart. Protect your body. Protect your game.