The Knee: Complex Yet Simple


I love a good oxymoron. Phrases like “jumbo shrimp,” “deafening silence,” or the fact that we “park” in a driveway and “drive” on a parkway, can really get us thinking!

But what if we applied that link of thinking to the body? Is there a joint in the body that can be described oxymoronically? According to Pete Egoscue, there is a joint in the body that provides us with a bit of an anatomical oxymoron. Check out this tweet:

Wow…both complex and simple at the same time? Just like “deafening silence,” Pete’s statement got me thinking. It got me investigating the knee joint more, and I wanted to share with you what I found.

We all know the knee is a hinge joint. Just like a door hinge, the knee is designed to flex and extend, to open and close, and there is little room for rotation. I say “little,” because the knee does rotate some, but when it rotates too much you get into trouble (think ACL–Anterior Cruciate Ligament–tear). As a result of it being a flexion/extension joint, the knee is considered a “stable joint” in the alternating stability-mobility pattern we see in the body.

Mobility StabilityThe knee is considered a stable joint, because its movement is limited to (basically) one plane–flexion and extension. The hip and ankle, on the other hand, are mobile joints. Not only do they flex and extend forwards and backwards, but you can also move the hip and ankle in a rotational plane and in a lateral (abduction/adduction) plane. And it’s because of this multi-plane movement that the knee’s role is so crucialThis is where the synchronization aspect Pete mentioned in his tweet comes in. It has to keep its design feature of being a flexion/extension joint. However, if and when the hip and ankle lose their mobility, lose their function, the roles become jumbled. The roles switch. The hip and/or ankle have become “stable” joints, and therefore, the knee becomes a “mobile” joint.

Let’s think in terms of a degenerative hip. As hip function become compromised, it starts to lose its designed range of motion (ROM). Yet the body knows that it needs that ROM and will make it up somewhere else in the body. Helloooooo, knee joint! Not enough ROM in the hip? Let’s add some to the knee! What could possibly go wrong? (Please re-read that last sentence with your most sarcastic of internal voices.)

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As an example of what can, in fact, go wrong, I know someone who recently tore his ACL, his lateral and medial meniscus, and strained his Medial Collateral Ligament (MCL) and Lateral Collateral Ligament (LCL). And all of that happened while exiting the batter’s box after getting a hit in a softball game. Do you think that maybe, just maybe, there were compensations and dysfunctions elsewhere in the body, specifically the hip joint? I sure do. No one should have their knee explode like he did simply by running to first base.  He quickly found out just how may components there are in the knee! That speaks to Pete’s “complex” joint comment in his tweet.

Yet the job of the knee is simple–flex and extend. But when the knee is asked to do more than it’s intended to do, trouble is waiting right around the corner, just like the guy in the example.

But where the “complex” aspect of the job comes in is that the knee has to “slow down” the faster moving, and far more mobile, hip and ankle joints. Check out what Pete has to say about it in Pain Free:

The knee is also an elegant solution to a fiendishly difficult problem. The hip and ankle move at vastly different rates of speed; their gears, if you will, vary in size. Their muscular power sources range from the equivalent of jet propulsion to rubber bands. Hooking them up together is at once madness and pure genius.

The knee is, essentially, acting like a governor on a car. It’s being asked to be the speed regulator. There is a TON of motion happening above and below the knee joint, and it’s stuck in the middle.

Like Pete said: It’s a complex and simple joint being asked to do a complex and simple job.

If you’re experiencing knee pain, chances are it’s not the knee’s fault. The vast majority of time we see clients who have pain in the knee, but the root cause is somewhere else. The knee pain is simply the effect. When we find the underlying dysfunction and correct it, the knee pain goes away. Eliminating the pain is simple. The good news is that it’s not complex.

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