Revisiting the concept of “hypermobile” and “hypomobile” SI joints

I recently heard from a reader who wasn’t sure if I had suffered from hypermobile or hypomobile SI joints.

The answer is both, of course!

However, I really appreciated this person’s email because it provided a little bit of a wake up call to me that maybe I need to do a better job explaining these concepts.   So here’s what I said– this reader found it helpful, and if any of you are wondering about this, I hope you will too!

The terms hypermobility and hypomobility can be kind of confusing because people use them to refer to different things– and all the different meanings are technically correct.

Essentially, if a joint is hypermobile, that means it’s moving too much (that’s what hyper- signals).

If a joint is hypomobile, that means it isn’t moving as much as it’s supposed to.

However, these words don’t reflect why a joint might be moving too much or too little.

I use these words in several different ways on my blog to reflect different aspects of my story.

An SI joint can become hypermobile after the ligaments have been sprained.  They aren’t doing their job to hold the joint in place, so the two bones that make it up (the sacrum and ilium) move too much, in relation to each other.  This creates pain and inflammation.

However. In some people, myself included, if the joint starts moving too much outside of its normal range of motion, the ilium can move too far backwards in relation to the sacrum and get “stuck” there.  This is what people mean when they talk about a “stuck,” “locked,” or “jammed” SI joint.  Technically, it’s hypomobile, because it isn’t moving enough.  However, it only got that way because it moved outside of its normal range of motion– originally, it was hypermobile.

(Here’s a post I wrote that explains the concept of a stuck SI joint in more detail).

The reason someone would have prolotherapy is to help tighten the ligaments back up so that they can hold the joint in place.  Technically, this can help to reduce both hyper- and hypo- mobility– if, again, you think about hypomobility as the joint moving out of alignment because the ligaments aren’t doing their job.

The right person to really evaluate you and explain this more, of course, will be the prolotherapy doctor you consult.  But I hope I’m helping to clear up some confusion.

The reason you may be confused is that I’ve also used the word hypermobile to describe the shape of my joints themselves.  This obviously the same word, and the same joint, but with a totally different meaning in this context (I know, it’s unfortunate!).

The reason I didn’t have prolotherapy is that I, like some other people, was born with actual joint shapes that make them prone to being unstable and easily injured.  Basically, the way my sacrum and ilium come together, they come together in a way that relies pretty heavily on ligaments to hold them in place and leaves them prone to injury, because they aren’t really lined up in an ideal way (if that makes sense).  It’s actually not just my SI joints that are hypermobile in this way– through genetic luck of the draw, I have knees, wrists, and elbow joints that all tend to be hypermobile, or “move too much.”  In my case, Dr. Borg-Stein (who I consulted for prolotherapy) was concerned that my joints wouldn’t be able to stay aligned for long enough after the injections for the ligaments to tighten up in the right position.

However, this hypermobility based on bone shape is totally different than the type of hypermobility I’m referring to when I’m talking about a joint that moves too much due to sprained ligaments.

I hope this makes sense (!).  I wish we had better terminology.

So in a nutshell, here the things I’ve been talking about:

-hypermobile joints due to bone shape

-a hypermobile joint due to sprained ligaments
-a hypomobile joint due to sprained ligaments that allowed the ilium to rotate backwards and get jammed against the sacrum.

Bone shape: There’s no way to change the bone shape you were born with, but this might not turn out to be an issue at all for you.  In all the people I’ve emailed and communicated with, I’ve come to think that I’m a pretty rare case here.  So I don’t want to freak you out unnecessarily– the right doctor can evaluate.

You can’t always control ligament healing, but you can help it along to an extent.  That’s why people try prolotherapy or PRP.  For me, because I wasn’t a good candidate for these injections, I was able to use muscle strengthening and modifying my movement patterns in a way that stopped continually re-stressing the ligaments.

Okay, so that is my whole explanation for now.  If any of you were curious about these concepts, I hope this helped.

Here are my previous two posts on these subjects:

If you have any questions, feel free to comment below or email me at!

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