Explaining the Non-Contact ACL Tear

Torn Anterior Cruciate LigamentThe knee joint.

Apparently, it’s fragile.

I wasn’t aware of it, but it’s becoming more and more obvious.

We shouldn’t run for fear of doing irreparable damage to it. We shouldn’t jump too much, because our poor little knee might explode. Even climbing stairs is frowned upon. My, oh my…how fragile we’ve become. I’ve blogged about the knee before, calling it “Complex, Yet Simple,” because it is. Sure, there’s a lot going on inside the joint, but at the end of the day it’s a fairly straight-forward joint (or at least it should be).

Yet there’s a term that is popping up across sports fields and arenas all over the world. It’s becoming more and more prevalent and is “confirming” just how fragile our knee joint is…

…the dreaded “Non-Contact ACL Tear!”

Yes, folks, we’ve become so fragile that there doesn’t even need to be an event for us to tear our anterior cruciate ligament (ACL). We used to hear about people tearing their ACL skiing or playing basketball or getting tackled on the side of the knee during a football game, but now we don’t even need contact to suffer a tear.

Before we get to why these non-contact ACL tears happen, let’s have a short anatomy lesson. The knee is primarily a flexion-extension joint. You flex your knee, bringing your heel toward your glute muscles, and when extending the knee, you move the heel away from your glute muscles. However, I used the word “primarily,” because the knee does internally and externally rotate. In addition, it has the capability to move in a varus- and valgus-stress (bow-legged and knock-kneed, respectively) manner.

One important element to keep in mind when talking about the knee and how it’s designed to function, is that the knee is going to do what the hip tells it to do. It will only be as functional as the hip is functional. It has a sort of “functional ceiling,” if you will, based on the capabilities and functionality of the hip. Remember when I blogged about The Importance of the Hip Flexor–if momma ain’t happy, ain’t nobody happy!

One of the really cool things about the body is that there is an alternating stability-mobility pattern throughout all of its joints. Starting from the ground and working up, the foot is a “stable” joint, the ankle is a “mobile” joint, the knee “stable,” the hip “mobile,” the lumbar spine “stable,” etc.


If one joint loses this alternating pattern, the body–although remarkable in its ability to adapt and change on the fly–can be in trouble. Take the hip, for example. Someone with a degenerative hip no longer has a “mobile” hip. Their hip has lost its designed range of motion. However, the body still knows that it needs that range of motion. So, what does the body do? In all its infinite coolness, it flip-flops the mobility-stability pattern. That’s right, as your hip becomes “stable,” your knee and your lumbar spine both become “mobile” joints…even though both are designed to be stable!

That herniated disc? You guessed it. Your lumbar spine became too mobile, and the disc herniated (by design, by the way) in an attempt to alleviate the undue stress and pressure it found itself under.

And, as for your knee? Contact or no contact, a hyper-mobile knee is an ACL tear waiting to happen. When there isn’t proper range of motion at the hip, the knee gets asked to help make up the difference. Not good, if you’re jumping, landing, or sprinting. Heck, it’s not good if you’re walking up and down the stairs. You see…it’s not that the knee is fragile, it’s that the body has asked it to do a job that it simply isn’t designed to do. What’s actually true, is that your body should be applauded for adapting to its surrounding circumstances. Yes, you blew your ACL, but your body was simply trying to get you from Point A to Point B.

A non-contact ACL tear is a direct result of insufficient hip function. When that wide receiver running routes in practice stops, plants his foot, and changes directions, it’s crucial that the hip, knee, and ankle all talk to each other. If they don’t, if the hip is dysfunctional, there’s a breakdown in joint communication. The receiver’s hip can’t functionally take the work, the knee is recruited to help, and the outcome is less-than desirable. To put it in layman’s terms: his body zigs, but his knee zags.

Bye, bye, ACL.

Bye, Bye, football season.

See you next year.

The unsuspecting player thinks that it was “bad luck,” or perhaps a “bad knee,” but that couldn’t be farther from the truth. What’s true is there has been a breakdown in the kinetic chain, and his knee was the fall-guy. The good news is that he’ll have plenty of time to reconnect the kinetic chain during his time off. And if he doesn’t want to be a repeat offender, it’s crucial that he do exactly that…starting at the hip.

QUESTION: What is your ACL story? Are you a repeat offender?