What is an “ACL” and Why is Everyone Scared of It?

The soccer industry’s biggest enemy is the ACL. Injuring your ACL will place your high school, collegiate, or professional career to a screeching halt.

And, once you experience it, it has a high chance of happening again.

So what’s an “ACL” and why is everyone scared of it? How do I avoid injuring it and protect my longevity in my sport?

The ACL – Explained

The anterior cruciate ligament, or ACL, is located inside your knee joint. It is one of the major stabilizing ligaments in the knee.

It’s main job is to protect the tibia (shin bone) from shifting forward excessively. It also provides stability by protecting the joint from rotational forces. Too much movement in the joint can damage the cartilage. Damaged cartilage is a precursor to arthritis.

Curtesy 3D4 Medical, YouTube

The ACL is extremely important in the integrity of the knee joint, especially in soccer, considering the demands on it.

The ACL helps passively stabilize the knee when you land, cut, and run. But it can’t do that job on its own.

There are many muscles that help actively supplement the ACL to help protect the joint from shearing forces. Your core (3), quads, hamstrings, and glutes are the biggest influencers in knee joint health, but research has been slowly uncovering other muscular links to knee joint health over the past 20+ years.

The body is a machine. The big toe can influence movement patterns in the hip. It’s amazing what kind of links you can find in the body when you look hard enough.

But, if the muscles aren’t helping to control certain movements, the ACL is in danger.

When the ACL Fails

The ACL is a passive stabilizer. Your muscles are active stabilizers. They work together to support the knee.

If your muscles are not working hard enough to protect your knee, then your ligaments will take on the load. Sure, your ligaments could take it… but not always. If you firmly tug on a rope frequently enough, it will eventually snap.

For example, if you’re on a hike that requires ropes to climb the rocks, how much do you trust that rope? How do you know that it won’t fail and leave you scrambling down a mountain? You simply don’t know how much load a passive structure can handle until it can’t handle any more load. Then, you have your answer… a little too late.

The ACL “rope” is firmly tugged with excessive forward movement and rotation of the tibia in the joint. Tug hard enough in that direction and it may fail.

When the ACL fails, you are left with less passive stability. Many times, your active stability was insufficient as well, which led to the injury.

Once the swelling and pain subsides, the knee can function, but not well. It gives out. It feels weird when you walk on uneven ground. It’s hard to go down stairs or walk downhill. It hurts to pivot. You can’t trust it when you run or jump.

And, now, it feels impossible to play soccer.

Am I At Risk of Tearing my ACL?

I know what you’re thinking. “Welp, tearing an ACL sounds rough. How do I not do that?”

Every step of prevention begins at understanding your risk factors. Research has been looking at these for years, and a few common themes keep popping up.

Here are the main risk factors.

History of a previous ACL tear

If you have any injury, you’re always at risk of a reinjury.

That’s because things don’t heal exactly as they once were. Scar tissue creates a weak point, like a crack in a mirror. Muscle/ligament fibers don’t align themselves exactly right when they regenerate.

However, your risk factor didn’t just increase on the same side as your injury. It increases on the OTHER side, too.

One of the biggest reasons is that the predisposing factors to your injury, whether it be anatomical predisposition or muscular imbalance, likely exists on the other side. Once your injury happens, it’s a hint that the other limb may be vulnerable, too.

Being a girl

Girls, I hate this one, too. But it’s true.

There’s a unique predisposition that girls have to ACL tears. Our pelvis is bigger than a man’s pelvis. That means our hips sit wider than men’s hips, creating a more dramatic angle when you look at your hip-knee-ankle relationship. Research measures a similar-but-different angle called the “Q angle”. Larger Q angles correlate with a more “knock knee” appearance.

That angle varies between girls’ anatomy. Not everyone is built the same. But, the bigger that angle, the more shear your knee may experience which can stress your ACL.

Compared to boys, girls have smaller areas and more dramatic slopes where the ACL attaches. Girls also have increased general laxity of the ligaments of the knee. Girls can’t help their anatomy, but they can improve the active stability that muscles can provide if they put in the effort. (3)

Neuromuscular Deficits

Neuromuscular control is the most “modifiable” risk factor which seems to have a huge impact on prevention. If it’s modifiable, then you can control it.

Neuromuscular deficits are likely the most common reason for ACL failure. That’s because 60-70% of all ACL injuries are non-contact. (1) Non-contact ACL failure occurs when running, cutting, or landing without influence from an outside force (like a collision with another player).

If your active stability (muscular control) is adequate, you’ll avoid high-risk joint positions that place stress on the ACL.

Poor neuromuscular control looks like quadriceps dominance, poor hamstring recruitment, poor single-leg balance, knee valgus with landing (knee falls inward), and ligament dominance (locking out knees, reliance on passive stability).

Posterior-lateral reach – part of Y-balance test and drill

What Happens If I Do Tear My ACL?

If you do tear your ACL, it will completely halt your athletic career for at least 8-12 months. There’s no sugar-coating it. As a physical therapist, I can confirm that young players are usually nowhere close to ready at 4-5 months out, which is usually when they hope to return.

I am the unfortunate deliverer of bad news. Please don’t shoot the messenger.

Although more recent research has shown advancements in non-operative rehabilitation of an ACL tear, it doesn’t necessarily apply to high-level athletes in their youth.

To ensure longevity in sport, young athletes need surgery to address the lack of passive stability. Extensive rehabilitation is required to improve active stability: from basic strengthening, to neuromuscular control and balance training, and finally to application of strength and control to game-like situations.

Return to sport depends on each person, but it generally takes 8-12 months. It is a long process, but returning too early will increase risk of re-tear. Trust me, you don’t want to start at ground zero just as you’re approaching 8 months post-op.

This is especially true of young athletes. Re-tear rate is very high in females and males, particularly under the age of 18. (4) This is due to a number of factors depending on graft type. Urgency to return to sport is a very realistic reason, particularly if collegiate or professional play is on the horizon.

Wiggins’ et al.‘s systematic review & meta-analysis (a very high-quality study indeed) identified that “…athletes younger than 25 years who return to sport have a secondary ACL injury rate of 23%,” which is significant.

That’s about 1 in 4 players. That’s craziness. Don’t return if you’re not ready.

And if your physical therapy stops because of lack of insurance coverage, get a thorough home exercise program to continue working towards return to play.

Here’s the general return-to-sport criteria for post-op ACL injuries: (1)

  1. 8-12+ months out
  2. No pain or swelling
  3. Knee range of motion is the same as the other side
  4. No signs of ACL laxity per special tests
  5. Near symmetrical single-limb hop tests compared to opposite leg
  6. Jump-landing shows no valgus (knee cave), including double-limb and single limb landing

Depending on the sport, there may be more specific criteria. Soccer may need more testing in the frontal plane (cutting, agility) before returning to sport.

Do ACL Injuries Affect College Recruitment?

Youth soccer players can absolutely return to an elite level after an ACL tear.

One large study of 500+ youth soccer players showed that the ACL surgery allowed return to full sport, however 1 in 4 of the players had another tear. (2) That’s very similar to Wiggins‘ findings mentioned earlier.

Coaches may not be aware of the stats, but if they’ve been in the industry long enough, they know what an ACL might mean for a player’s future.

Some coaches will look for a different prospect, and some will still be interested. The decision largely depends on the team’s needs and the coach’s willingness to gamble for a great player. Remember – their decision to recruit you can influence their success, the school’s ranking, and the coach’s career. It’s a business decision.

A big injury like an ACL tear can be detrimental, but it doesn’t have to be. That’s why it’s important to have excellent academics and good character. Coaches are more likely to keep you in their sights if you can offer more than athleticism.

A sudden injury, combined with poor grades, will deter a coach very fast. Never rely on one thing alone to get you far. Diversify your strengths, and you’ll be more valuable to a coach, even with an ACL injury.

So How Do I Avoid an ACL Injury?

It’s not difficult to implement injury prevention into your soccer training.

Teams don’t always prioritize this, especially in youth sports. You need the discipline to seek prevention on your own.

BTW – hey, coaches – do more injury prevention with your players! Protect your athletes.

ACL injury prevention works on the following:

  • Acceleration and deceleration
  • Control of rotation and anti-rotation motions
  • Double-limb and single-limb landing
  • Coordination of core with limb movement
  • Control of lateral movements
  • Multitasking with movements
  • Education on recovery, cross-training, and movement patterns

If you want to get started on personalized injury prevention that you can easily perform at home, check out Integrative Soccer’s Injury Prevention Program and work with Coach Nicole (me) on your specific vulnerabilities and goals!

ACL Injuries Are Scary, They Aren’t the End

You can prevent most ACL injuries, and if you do suffer from it, it’s not the end of the world.

But, it’s not an injury to take lightly. Recovery is long and it can happen again.

If you’re concerned about your ACL’s vulnerability, do something about it before it’s too late. Get an assessment, start training, and prevent injury.

Cited References

  1. Raines BT, Naclerio E, Sherman SL. Management of Anterior Cruciate Ligament Injury: What’s In and What’s Out? Indian J Orthop. 2017 Sep-Oct;51(5):563-575. 
  2. Sandon A, Söderström T, Stenling A, Forssblad M. Can Talented Youth Soccer Players Who Have Undergone Anterior Cruciate Ligament Reconstruction Reach the Elite Level? The American Journal of Sports Medicine. 2021;49(2):384-390.
  3. Smith HC, Vacek P, Johnson RJ, Slauterbeck JR, Hashemi J, Shultz S, Beynnon BD. Risk factors for anterior cruciate ligament injury: a review of the literature – part 1: neuromuscular and anatomic risk. Sports Health. 2012 Jan;4(1):69-78.
  4. Webster KE, Feller JA. Exploring the High Reinjury Rate in Younger Patients Undergoing Anterior Cruciate Ligament Reconstruction. Am J Sports Med. 2016 Nov;44(11):2827-2832.
  5. Wiggins AJ, Grandhi RK, Schneider DK, Stanfield D, Webster KE, Myer GD. Risk of Secondary Injury in Younger Athletes After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis. Am J Sports Med. 2016 Jul;44(7):1861-76. 

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