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Why Did My ACL Tear?

Risk Factors and Mechanisms of Injury

By Blake A SwanPublished about a year ago 14 min read
Why Did My ACL Tear?
Photo by Marcel Strauß on Unsplash

My last post focused on what it means to tear your ACL and what to expect with the recovery process.

In part two of this series, we’ll examine why your ACL tore. Now, I know you remember how you tore your ACL. Even if you had a partial tear, and you could still function, you know what you were doing when it happened. You felt it pop, felt it twist, and maybe even hit the ground.

Today, we are going to discuss the ways our body may be compromised. Going beyond the mechanisms of injury. Which is very important to discuss before and after you have the knee injury. Understanding the factors and environments that may predispose us to a knee injury. If we fail to address them, we are still at risk to recreate the same conditions that resulted in our injury.

Warning signs of a knee injury.

Having worked in strength and conditioning for over a decade, I have seen a lot. Add in working at an orthopaedic office for nearly a decade and I’ve seen almost everything. I’m going to give you the most common signs of a knee injury on the horizon. Discussing what these signs, symptoms and environment that put you at risk. These include but are not limited to: Previous Injury, Problems at the Knee, Fitness and your Movement Patterns.

Previous Injury

By Jeffrey F Lin on Unsplash

The greatest predictor of an injury is a previous injury. The body suffered damage and perhaps your muscles are tighter and weaker than before. Perhaps your joint is loose and there’s too much motion and it’s hard to maintain joint integrity because of it. That’s not the biggest problem. Your previous injury may be an indicator of a more serious condition. Improper mechanics may create excessive stress on your body. To explain this, we will discuss the two types of injuries you can suffer.

Acute Injury vs. Chronic Injury

Think of an acute injury as something that happens in a moment. You stubbed your toe or you drop a weight on your foot. The happened in an instant and you can easily recognize the cause of injury from the moment it occurred. A chronic injury is an injury that sticks around for a while. You’ve had that nagging knee pain for years, but you live with it. Your shoulder hurts every time you throw, but it comes and goes. The deceiving thing about chronic injuries is that you may “feel” fine and continue doing the activity.

You’re actually hurting yourself, and making it worse.

The body makes adjustments to keep you functioning and minimizes your pain. One day, your back gives out when you reach for a pen. It didn’t give out because the pen was super heavy. This isn’t the first time you tweaked it. For years, your back has endured your poor movement patterns. This was the one millionth tweak, and it finally gave out. Is that really an acute injury?

Wear and Tear

We experience microtrauma regularly. Moments of stress our bodies are handled without us even noticing there was a problem to begin with. Just look at your clothes. The sole of your shoes are worn out on one side more than the other. Your insole matches, with one side being rubbed smooth. The same goes for your shirts, your pants, your chairs. Your body displaces weight in a unique pattern. This pattern may put excess stress in specific areas of your body. It results in pain and discomfort.

You suffered from tight hamstrings and quad strains that compromised your legs before you got hurt. Pain you ignore until the stress results in a significant injury. Perhaps it’s knee pain that finally culminates in you tearing your ACL. It could actually be back and hip pain that you experience before suffering an ACL injury. It could even be your other leg that was bothering you first before you got injured.

You were so focused on a specific part instead of paying attention to the whole.

Next post, we will go over how to identify if your body is at risk.

Today, what I need you to consider is that your movement pattern may be the cause or chronic pain and an acute injury. Without being addressed, the method or mechanics of injury will be repeated and it’s a never-ending cycle of pain. Acknowledging that your previous injury history may be evidence of improper movement patterns. Repeating the stress within this pattern predisposes you to injury.

Problems at the Knee

Cold, Stiff Joints

Not all of you may be old enough to understand the feeling of waking up and your body being stiff. Not tight, but stiff. Meaning that part of your body won’t work for at least another hour. Perhaps you may wonder why it always happens when you wake up in the morning. That feeling of waking up in the stiff is the easiest way to describe the feeling of being “cold joint.” The blood has settled in other parts of your body, except the parts you need when you have to move.

This is a very simplistic explanation of how and why your body gets cold, but for our needs, it will do.

Now, imagine your athlete has been sitting all day. To expect them to jump up and compete is unrealistic. With youth, the body will bounce back even in suboptimal conditions.

When you’re young, your body physiologically is more pliable. Allowing you to get away with not warming up properly. To a point. As competition levels increase and the demands for performance increase exponentially. We don’t have the luxury of warming up during the game. Taxing the body to this extreme becomes a major hazard. Those that last the longest rely on raw athleticism and/or conditioning. As some of you have learned the hard way, that is not enough to prevent injury.

Remember the last time you played pickup with your friends? Or toss a ball around with your kids?

The next day you were so sore you thought you broke something. That’s because you have a cold muscles and cold, stiff joints.

The purpose of the Warm Up is to prepare the body for activity. Not just any activity, it’s supposed to prepare you for the specific activity you are about to engage in. This includes raising the body temperature. Rehearsing the movement patterns progressively, eventually matching the intensity of your activity. Warm-ups will minimize the risk of injury for sports, even if you have a stiff joint. However, more work needs to be done if you have a stiff joint.

Am I Tight or am I Stiff?

Time to know your terms. People use tightness and stiffness interchangeably, but I’m here to tell you they are not the same. Here’s a simple test to identify if you’re tight or if you’re stiff. If able, try to touch your toes. Now, for those of you cannot touch your toes, here comes the difference. If you are tight, you can inch closer. If you are stiff, you can’t move any further. Even if someone tries to push you further, you won’t budge. There are people that will tell you that “I can’t move further” and they mean it. Here’s why:

Tight, or tightness - when your tissues are shortened. Whether through activity or inactivity, they have shortened themselves and you can release them through stretching or activity.

Stiff, or stiffness - when your body has made an adaptation in order to protect you. To maintain the balance of the system and avoid a traumatic failure, your body will not allow you to enter that range of motion.

Again, with stiffness, even someone pushing on you won't make a difference. Your body will be stuck in the same position.

Neither of these conditions is optimal for activity.

While we may play through it, it’s not ideal. We are simply adding more stress to the body and warping it even further. Eventually, the structures your body is relying on for support will fail. This results in an injury. Thus, the activity you’ve been doing for months and years improperly has finally caught up to you. It might not even occur during a challenging moment. Much like the person who hurts their back picking up that pen from before or brushing their teeth. It’s a culmination of things that lead you to be in this position. We will talk about those next.

Fitness and Movement Patterns

If you don’t use it, you lose it. That’s true of the human body. Detraining starts as early as two weeks. Meaning that in two weeks of inactivity, your body will begin regressing from where it once was. This is very important for athletes. We’ve talked about the condition of the knee but what about the condition of the body? Which is the foundation for movement and skill development.


In my podcast on Defining Your Terms, we discussed the difference between being fit and being fit for sport. Being fitness is a word we used to describe a baseline level of conditioning. For health, this includes cardiovascular health, body composition, flexibility, muscular strength and endurance. That’s health related fitness. Now, we have performance metrics of fitness that include coordination, balance, speed and agility, etc. Already, we have a wide variety of ways we can describe fitness. With that in mind, you can understand that being fit for healthy doesn’t mean you’re fit for sport.


We discussed this last week. Just a little blurb to remind you that having the wrong equipment also puts you at risk for injury. Worn out shoes or cleats. Using the wrong shoes on the wrong surface. Restrictive clothing or improper clothing for the weather. If you don't have the right equipment, you are putting yourself at risk.


When we look at Sumo Wrestlers or lineman in football, many people assume they are not fit. A sign that they themselves have limited knowledge of the subject. They are fit for their sport and activity. The mass that they can carry and the ability to maneuver it is a necessity.

It is does not mean that they are sloppy or lazy.

Many are leaner than you expect and in phenomenal shape. Many are surprised when they discover that these human giants shrink once they leave the sport. Even more are amazed by the athleticism of Sumo wrestlers that are more agile and flexible than you imagine. Would it make sense for you to be 80 pounds lighter when your position requires you to explode into your opponent?

Understanding that each sport requires a specific level of conditioning, we can now understand the importance of being fit for sport. If you need to sprint often, then you should have sprint endurance and the ability to recover quickly.

Sports performance involves conditioning you to be athletic in the range of motion required for sport. If you need to do a full squat to jump high and I can jump from a half squat, I’m winning every time. Even if you’ve trained to change your technique, with fatigue, you will revert to that useless deep squat to jump. Without that conditioning, everything falls apart. It’s impossible to maintain form when you’re tired. Poor form means you will lose control of your body, which maximizes the stress and strain you put on your body. Even worse, your movement patterns are compromised and the compensation you make gets engrained into your body.

Movement Pattern Issues

Everything we do follows a pattern our body has adapted. How we walk, sit, stand, run, jump, type, all of it is a pattern our body has adapted to help us with the activity.

Which relaxers the strain on our brains because we can move without thinking. We don’t think about how we stand or walk. We don’t think about how we text or type. In sports, the ability to move and trust in that movement allows athletes to process an enormous amount of information and respond to it. They make it look effortless.

Patterns that get engrained into your body can be helpful, but they can also be harmful. If we are rehearsing the wrong way, are we really getting better? No. We are compromised. While it may feel better at the moment, we are increasing the stress on our body. When it reaches its peak, we get an injury.

Position that increases the risk for an ACL Injury

The biggest concerns we have is the valgus collapse and the distance between your center of gravity and your knee. If your knee buckles, which is a sign of ligament stress, you’re not using your muscles to support your movement. All that stress will pull on the structures designed to keep your knee stable. Then, you have the distance of your knee from your center of gravity. Excessive lunges forward, or a giant cut laterally can put too much stress on the knee.

The distance from the knee to center of gravity laterally put too much stress on his knee to try to fight his forces and the forces of the offensive player.

There are ways to assess movement patterns.

Here are just a few of the things that we look for as a risk factor for ACL Injury. Check out my podcast for more in-depth explanation of each.

  1. Quad Dominant
  2. Ligament Dominant
  3. Leg Dominant
  4. Trunk/Hip Flexor Disfunction
  5. Sprint Mechanics
  6. Landing Mechanics
  7. FMS Screening

Muscle Activation

Another issue that may arise is what we refer to as muscle activation. This may be in response to an altered movement pattern or it may have been an issue prior to injury. When we say a muscle is not “active,” it means it’s not contracting when we need it to contract.

My favorite example of this is when Tiger Woods.

Faced with a rain delay he eventually had to withdraw from a tournament. Foreshadowing future troubles in his career. When asked why, he said that “his glutes turned off” during the delay. Many people were confused. How do you glutes turn off? Well, with years of activity, stress, and injury, Tiger Woods’ glutes stopped engaging.

Meaning that he relies on other muscles to do the work meant for his glutes. A pattern adaptation that can ease your pain in the short term. However, it’s difficult to engage your “core” without your glutes. Your thigh muscles, like your quads, can’t replace your glutes. Considering your hip and hip muscles are the powerhouse of your body. You can’t replicate that and in deed he suffered pain that forced him to withdraw. He's had numerous injuries related to playing through injury and pain.

How does this impact you?

Well, first, most of us that sit for a prolonged period know the pressure it puts on your back. This is because sitting causes several issues for your body. One of those issues is your glutes turning off. Without glute support, your back has to do more work. Work it is not intended to do. Another reason that simple glute activation exercises can do wonders for people who are experiencing back pain.

Back to the ACL

Overactive quads, inactive hamstrings and/or glutes are a recipe for disaster. There are not enough forces to counterbalance the stress on your knee. There's too much pressure on one direction of your body. Add in the fatigue factor. Now, your fatigued body and overworked muscles are creating tension at the knee. Limiting the joint space and eventually that restriction transitions from tightness and becomes stiffness. Meaning you’re one wrong step away from injury.

By Lindsay Henwood on Unsplash

Two Down, One to go!

Today, we’ve discussed a few reasons you may have torn your ACL. Understanding the factors inside and out. Hopefully, you will take this information and be proactive about your health. Recognizing the importance of conditioning. Focusing on your warmup and taking it seriously as a method of preparing for competition and preventing injury. Before you engage in an activity, you should have your movement assessed to ensure that your moving optimally. Or optimal enough to take part in sports.

Questions, Concerns, or If you're interested in one of my lectures, please feel free to contact me. You can also check out our podcast, BeattheBS Challenge here for more topics.


About the Creator

Blake A Swan

NCSA Strength and Conditioning Professional certified as a CSCS, TSAC-F, and CPT. I have my FMS Certification as well, and spent over a decade working with athletes in various sports. Including youth, high school, college, Olympic and Pro.

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