Can an ACL Tear Change Your Brain?

An injury really can change a life if it's serious enough. But what about the person inside the life? A tear to the anterior cruciate ligament (ACL) can be life-changing, especially for athletes as it causes long-term challenges and may be enough to throw a person off of their sport. But it may surprise you to learn that in some cases, it might even cause long-term changes to the brain. 

Torn ACL Has a Shocking Reinjury Rate

The ACL crosses just below the front of the kneecap, stabilizing the knee, so it can handle quite a bit of stress from running to skiing. ACL injuries usually occur during high-energy sports that require quick stops and turns, although any sudden, intense blow to the knee can do the trick, according to Mayo Clinic. And suddenly you're laid up for weeks and in for a long road ahead.

For people who can rest the joint while it heals, physical therapy and reduced activity may be enough. But if more than one ligament is injured, or if the person does not sufficiently allow the tear to heal itself — which is all too often the case of athletes, who want or need to be back on their feet as soon as possible — surgery may be necessary. 

For reasons only recently explored, reinjury to the ACL is ridiculously high. One study found the rate to be 23% among patients younger than 25 years old. Other research shows that the rate could be as high as 40% among those 18-19 years old. This could indicate a connection between higher activity levels and reinjuries, but age and activity levels aren’t always the only factors at play.

ACL Tear May Cause Unexpected Changes to the Brain

An injury to the knee can sometimes affect the body all the way up to the brain. People who’ve recovered from ACL injuries may find their muscle memory in the torn knee lacking, which can affect motor function. As a result, the recovered knee, even after it’s fully healed, may be more accident-prone going forward.

But one study just published in NeuroImage: Clinical may have pinpointed the cause. Using advanced brain imaging techniques, researchers have found areas where the actual nerve pathways appear to weaken as a result of ACL tears. This can lead to visible differences between the regions of the brain controlling the good knee versus the injured knee. 

Additional research has shown altered gait and other forms of compensation could redirect the brain to focus on muscle groups that can help the injured area recover, neglecting areas it would normally use to move. This may be the brain’s attempt to force rest on the injured ligament. However, when the knee gets put to regular use once again, it may be clumsy and unusually weak. These changes can remain years after the initial injury.

Recovering From an ACL Tear

Reinjury prevention may require more than rest and physical therapy. To fully recover the ACL, patients may also need to extend the treatment to their minds. Adaptations that force patients to engage their sense of movement and feel, incorporating use of blindfolds, shifts in focus and biofeedback, for example, may help the mind rewire lost pathways even while the knee heals. Unlike traditional physical therapy for this type of injury, an approach that works both to heal the injury and reorient the brain to the feel of appropriate muscle groups could be one key to improving recovery rates.

An ACL tear can turn into years of pain for some people, with changes in the brain contributing to a high reinjury rate and extending recovery times. New approaches to treatment in sports medicine could soon mean that everyone has a better chance of recovering fully and in a timely way. Mind-body treatments may be the future in healing far more than torn knee ligaments, too. We’ll be sure to share the updates as they come.

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