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ACL Tears Are Brain Injury's

Updated: Feb 11

Not literally a traumatic brain injury, but a ACL tear has a long term impact on the brains wiring and firing. If this is not something we address in ACL rehab early and often it can result in long term compensation and increase the chances of re-injury.


The ACL is chock full of these fancy things called mechanoreceptors. They tell the brain where the knee is in space unconsciously. Before, an ACL injury you don't think about where your knee is in space because your mechano buddies stored in the ACL are constantly relaying information to the brain about where it is in space without any conscious control from you.

After an ACL tear your brain kind of freaks out. It has lost a major source of sensory information and to keep you safe from further injury essentially shuts down the quadriceps muscle. What you once could do unconsciously now requires high degrees of conscious control and focus. This is a dangerous pattern to get into.


The body is master compensator, so it finds away around these new deficits, but they are not in best interest of someone rehabbing back from an ACL injury.

1. Internal Focus: Your body now requires conscious control to fire muscles and stabilize the knee. What was once able to be performed without ever giving a thought now requires a lot of internal concentration and focus to perform.

2. Visual Dominance: The body lost its sensory supply it used to rely on for information on knee position. Now vision picks up the slack. We see an over-reliance on the visual system to fire muscles and find stability.

3. Cognitive Load: Due to the above factors we have limited space in our attention space for competing stimuli. We must assign additional attention resources to figuring out where your knee is in space, firing a muscle, and stabilizing the knee resulting in decreased "room" for other cognitive tasks (reacting to a defender, catching a ball, shooting a ball, passing to your teammate, coach yelling at you, etc).


While your body is great at compensating to survive, this is not optimal for return to function/sports and leaves us at an increased risk of re-injury.

Sports are incredibly chaotic. They require the processing of hundreds of decisions within milliseconds, many of which are reflexive and involuntary. However, if you still require conscious control of your knee, sport will require and force you into situations where you can not think about the knee. If you have never been exposed to this level of cognitive load or distraction then you will not be prepared for it. Your attention can only be subdivided so many times before you start to break down. The over reliance on the visual system is also an issue as you will not be able to always double check with vision to stabilize your knee. Sports require a "head on a swivel" you do not have time to visually guide yourself through sports.


No you are not doomed! We can fix it, however we MUST address it. It is not something that just comes back on its own. Like I mentioned earlier, your body is a master compensator and we can help the body compensate in the right direction versus the harmful direction as discussed above.

Down Regulate Vision:

As we discussed earlier the visual system takes over. We can help decrease this take over by simply taking away or decreasing vision. They make expensive glasses that help with this however, a free solution is simply performing tasks with the eyes closed. This forces the body to rely on the sensory system to find itself in space. Here is an easy example:

Up Regulate Sensory:

We need the sensory system to pick up the slack from the missing ACL mechanoreceptors. An easy way to do this is again to take away vision as discussed above. Another way to help out the sensory system is by not taking it away. I am referring to unstable surface training. The common thought process is "I am going to improve stability by making them unstable". This is incorrect logic. By un-stabilizing someone they will rely on their vision and vestibular system MORE to find stability. That is the opposite of what we want. Give the sensory system a chance by doing exercises on solid ground and challenging the vestibular and visual systems.

Dual Task:

To combat this very internal focus where we constantly are thinking about our knee, dual tasking is essential. This brings your focus our into the external environment rather than only focused on the knee. This can look like anything really and you can get pretty creative with it. For example, you can do virtual reality of someone kicking a soccer ball while performing leg extensions. There are cheap options on amazon called Google Cardboard. You could spice up your single leg balance by playing catch or performing headers. You could perform other tasks during single leg balance or a sport specific tasks. I love the stroop test which is a fun brain game you can find on youtube.

Really you could do anything to bring your attention from internal to external.

Hopefully that helps you understand some of the issues and gaps in our current ACL rehab as well as what you can do about it. Just a reminder we have an ACL Home Exercise Program available that allows you to make progress at home!


Need sports medicine physical therapy? We are located near North Canton/Akron, OH and would love to work with you.

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