What are the three types of bone edema on MRI in a runner with a stress fracture? Well, that is what we’re talking about today on the Doc On The Run Podcast.
I was just on a call with an injured runner who had what they thought was a stress fracture and we were talking about the way it shows up on an MRI. Everybody thinks MRIs are perfect and they give you all this information.
It is true that there is a tremendous amount of images and information that you can get from an MRI but you have to understand that most of the imaging of bone on MRI is not really looking for a crack. It’s looking for trouble in the form of inflammation or edema within the bone. An edema is just the medical term for inflammation. So, I thought it might be useful to talk about the three types of inflammation or edema that you can see in a bone on an MRI.
Let’s talk about this. So, let’s say you have a stress fracture in your tibia. All right, the tibia looks like this and let’s say you have pain right here in the middle of the tibia and you think you have a tibial stress fracture. Okay, so we take the tibia, and you look at it in cross section. It’s going to look something like this where it’s kind of round, kind of triangular depending upon exactly where you’re looking at it. And then you have a couple of different things. You have the cortex, or the outer rim of the bone and you have the medullary canal in the middle of the bone.
So, this is bone marrow inside here. It’s soft. It’s mostly fat. And the outer part of the bone is a hard shell. It’s got calcium in it. It’s very firm. It’s very hard. That is why when you push on the front of it, it feels hard. Then you have a very thin layer on the outside of the bone called the periosteum. The periosteum covers the bone and that is on the outside. And it’s really adhered firmly to the bone. So, I’m just drawing it sort of with a little bit of space. That space does not really exist, however.
The three types of inflammation that you have. The first one is what we call. let me do it three ways. I’ll draw the same thing three times. That’ll probably be better. Okay, so you have the shell of the bone, the cortex or shell, outer rim. That is the cortex. You have the periosteum, the little fibrous layer that covers the bone and then you have the medullary canal in the middle, the soft part.
Okay, so it may not surprise you to hear that there are three specific parts, right? You have the periosteum. You have the cortex, and you have the medullary canal. So, when you get a stress fracture, there are sort of forms of stress fracture that can show up on an MRI.
The first one is where you have inflammation or fluid accumulating between the bone and the periosteum and it lifts up sometimes. It makes it sort of stick out or bulge out and you may see this on an MRI report as periosteal reaction. This is one of the things that you see that is one of the first things that happens in a stress reaction where you don’t have a crack in the bone. You just have the initial signs of inflammation happening between the bone and the periosteum.
The second one is where you have inflammation that shows up as bright white on your MRI inside the medullary canal. And that one is medullary edema. The third one, which is worse, is when you start having inflammation in the cortex of the bone and that is cortical edema. You will almost never see cortical edema without also having medullary edema and having the periosteal reaction. So, generally speaking, they’re progressive. They’re kind of additive. You get periosteal reaction first. Then you get medullary edema and then you get cortical edema as well.
The reason it’s a problem is that if you continue to ignore this and you’ve got increased inflammation in and around the bone with the cortex of the bone, that increased blood flow that puts the fluid in there that you see on an MRI is what eventually leads to the dreaded crack in the bone. But these other things come first.
So, that is what you’re looking for on an MRI. If you see these terms, cortical edema, medullary edema, periosteal reaction, they just signify different stages or gradations of the inflammation on the MRI in or around the stress fracture.
If you want to learn about the strategies I use with runners who have these kind of injuries and want to continue to run, I present all of that to you for free in the Stress Fracture Masterclass for Runners. You can get that for free at www.docontherun.com/stressfracturemasterclass. So, come check it out and I’ll see you in the training.
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