What’s the difference between a ligament sprain and a muscle strain?

Hey everyone,

Here’s a concept that comes up all the time, so I wanted to take a moment to clarify it.

What is a ligament, and what is a tendon?  And what happens when we injure each one?

A ligament is a very tough band of connective tissue that connects one bone to another.   Ligaments are what stabilize the SI joint (along with our muscles).  When a ligament is injured, it’s called a sprain.

So, when we injure the SI joint, it means we’ve sprained the ligament that hold the joint together.

This is different from a muscle or tendon strain. 

Tendons are also made of connective tissue, however, they connect muscle to a bone.  Therefore, every muscle has a tendon at either end.

Here is an illustration depicting an Achilles tendon tear, which is a common injury as far as tendon injuries go.

You can see how the tendon is the white part attaching the muscle to the heel bone.

Generally, for the purposes of the SI joint, we are really more concerned with ligaments.  

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When the fibers of a ligament are sprained, it means they are subjected to forces greater than they’re able to handle, and they can stretch and/or tear.

As I learned in my anatomy classes, the unfortunate reality is that ligaments are not always able to “tighten” back up after they are stretched out.  They don’t get much blood supply, which is why they can take a long time to heal, and don’t always heal completely, remaining vulnerable to re-injury.

This is why you may have heard people say it’s actually better to break a bone than injure a ligament.  Although bone breaks are obviously way more painful, bones actually do a much better job of healing, whereas ligaments may never completely heal.

A sprained ligament may always be slightly stretched out, which means it doesn’t do its job of holding two bones together as well as it should.

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Most of the articles I found explaining ligament injuries are about ankle sprains, because that’s one of the most common ligament injuries.  (Knee injuries are also a pretty big one).

But ligaments are ligaments, so what you read about ankle or knee ligaments being slow to heal is also true for SI joint ligaments.

Here’s an article from Physio Works which describes the three “levels” of ligament injury:

  • Grade l : Mild ligament tear
  • Grade 2 : Moderate ligament tear
  • Grade 3 : Severe (Ruptured) ligament tear

When a ligament is torn completely, as in the case of a Grade 3 tear, it requires surgery, because the body doesn’t have a way to reconnect the two ends without some help from a surgeon.

However, I’m really just telling you this for educational purposes– I don’t want to scare you.  In all of the research I’ve done, I haven’t heard of Grade 3 sprains for SI joint ligaments; it doesn’t seem likely given the biomechanics of the joint, or the way injuries to it would occur.

Instead, with the SI joint, it seems that Grade 1 or possibly Grade 2 injuries are enough to cause dysfunction.

People do have surgery for the SI joint, but these procedures are not traditional ligament repair surgeries.  Instead, the surgeon adds in screws or another device to attempt to hold the sacrum and the hip bone together, to make up for the fact that the ligaments are no longer doing their job adequately.

The point of the surgery is to work around the sprained ligaments, not to try to repair them.

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However, surgery is not your only option.  Ligaments do heal to an extent, and if you’re like me, it’s possible that by letting your ligaments rest, and building up enough muscle strength to take over, you can stabilize your joints again.  (You can check out my Key Points series, which explains more about how I did this).

I have also heard stories of patients having success with prolotherapy– a relatively new (and somewhat controversial) treatment that is meant to increase the rate at which ligaments heal.  (I have written about my consultation with a prolotherapy doctor here).

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So, hopefully this article provided a good overview for you of what ligaments are, and what your options are for healing.

For more info on ligaments:

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