The SI Joint and Shock Absorption


Hi everyone!  Here’s a new concept I haven’t written about as much yet.  I find it really interesting, and I hope you will too!

What I wanted to talk to you about is the SI joint’s role in shock absorption.

The SI joint is different from a lot of other joints in the body, in both its form and function.  (These are the official terms you’d learn in an anatomy class!)

What this means is that the SI joint has a pretty unique shape, compared to other joints in the body, and also that it has a unique job to do.

One of the SI joint’s main roles is shock absorption.  This is sort of similar to what people mean when they talk about shock absorbers in a car.

In a car, as in people, a certain amount of force is going to travel up the tires (or legs) as we move over the ground.  There will be more force if we’re moving quickly, and particularly if we hit bumps– or land harder on our feet, as in the case of running.

So one role of the SI joint is to receive some of this force that comes up the leg when we walk, run, or jump, and direct it in controlled way as it continues up the rest of our body.

We don’t want a ton of force to hit any one part of our body in one targeted spot.  For example, we don’t want all of the force of our foot hitting the ground to be directed to a one-inch spot on one of our lumbar discs.

Much better, instead, to have some “give” at the SI joints, which can spread that force out over a much larger area throughout our pelvis and trunk, so that the amount of force that hits any one small area is greatly reduced.

Now, once in a while, I read an article by some skeptic in the world of PT or a related field, who claims the SI joint doesn’t really serve a function.

Now, I will link to an article from a reputable source later in this post, because I believe in backing up what I say.

However, I can also tell you that I’ve experienced the role of SI joint as shock absorber in my own personal life, and I think it’s 100% real.

How do I know?

Pay attention to how your SI joints feel when you’re riding in a car.

When my SI joints are in place, I can go over a bump and feel almost no pain.

However, during my five-year saga, when my joints were really out of place, I would feel every little bump and dip in the road.   I’m talking everything.

If no one was behind me, I’d go about 10 miles under the speed limit, taking care to purposely avoid roads where the pavement was really torn up.

When I started to get better, I started to notice I was driving a lot faster.  Not that I advocate speeding– I’m simply saying that the pain that had served as a reminder for me to slow down was gone.


It’s because, with my SI joints in alignment, my body was finally able to distribute forces efficiently again.

When one of my SI joints were locked up, the force of going over a bump wouldn’t get dispersed properly.  The joint needs to be in place to do its job– otherwise, that force didn’t get directed the way it was supposed to, and I’d feel it in the joint.

But with the joint in alignment, I stopped really noticing the bumps in the road.  I didn’t even notice the change consciously at first– it’s just that all of a sudden I found I was able to start going the speed limit again, and 40 mph no longer seemed impossibly high.

This is something you might be able to notice in yourself.

I know that some of you aren’t really able to tell when your SI joints are in alignment or not.  I think that, in part, this is because some people have symptoms that are due more to inflammation in the joint, rather than the joint being out of place itself.

But for those of you whose symptoms do involve the joint moving out of place, you may find this is something to pay attention to.  Are there days when you find riding in the car to be much more painful than others?  This could be a sign that your joints are out of alignment.

The SI joint as Shock Absorber

For more, check out this great article from Taylored Training and Fitness (the link will take you to my notes on it, as well as the article link).

Here’s an awesome article, How Your Butt Can Hurt Your Low Back, from TIME magazine.   It quotes Dr. Alice Chen, a physiatrist at the Hospital for Special Surgery in New York City, on the role of SI joint as shock absorber.

Lastly check out Ask the Expert: What is the Sacroiliac Joint? from Spine MD.  It features Dr. Brian Subach, neurosurgeon and spine specialist, also describing the SI joint’s role in shock absorption.

Okay… that’s all for now! 

I hope this concept made sense!  As always, if you have any questions, you can email me at, or leave a comment below.


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