How can a bone stress reaction turn into a malunion, from running? Well, that’s what we’re talking about today on the Doc On The Run Podcast.
I was talking to a runner the other day who had a great question and he had heard something about a malunion and heard that this was a really bad thing. Well, he’d been diagnosed with a stress reaction in one of his metatarsals. So, he wanted to know, “If I run on it, is it going to turn into a malunion?” Okay. Well, the first thing is malunion is another one of these terms, that we as physicians use, that often confuse people.
So, union is when something joins together. When you have a fracture, the bone is cracked and it’s in two pieces. There’s one piece and there’s another piece. When they form a union and actually heal, well, everything’s good, it’s all healed. When you get a non-union, it’s where they don’t heal. They remain in two separate pieces, and the healing process eventually stops and your body gives up trying to fix it.
When you get a malunion, it means that the bone is healed. It’s actually united, but it’s in the wrong position. So, the bone, instead of being straight and healing straight, well, let’s say it’s crooked. And then it heals and it’s crooked. Well, that’s not actually good, right? It’s in the wrong place. So, your foot is designed to take the stress and strain of you walking, and running, and standing. If you have a bone that’s out of position, it’s either pointing down to the ground and it’s going to have too much stress on it, or, more commonly, it’s pushed up away from the ground because you ran on it or you stressed it, or you pushed on it, or you bent it, or something. And now, when it heals in the wrong position, it’s not doing its share of bearing the weight of you standing and running, and so the other bones get more stress and they actually become more at risk of getting a stress fracture later.
How does this happen? How does a stress reaction turn into a malunion? Well, it’s really simple. A stress reaction is where you have inflammation within the bone, the blood flow is increasing within the bone in response to this stress that you’ve applied to it. Training, running, box jumps, whatever. But what happens next is that the bone, because it gets weaker, because of this increased blood flow that’s trying to make it recover. Well, if you keep applying stress to the injured bone, in the same way, while it’s going through that process, it actually will get weaker and then it can crack. When it cracks, now you have a stress fracture. If you keep moving, if you keep stressing it, if you keep pushing on it, if you keep running on it, if you keep doing box jumps or jumping rope or something like that, well, then what’s going to happen is that bone, that is cracked and was in the right position, is going to get pushed right out of the right position, and it’s going to be in the wrong position.
Then, if you finally rest and you just leave it alone, and you let it heal in that wrong position, you have a malunion. It’s now healed, but crooked. That’s a problem. So, that’s the way it works. You get a stress reaction, and you keep stressing it, it cracks, it moves out of position, and then it heals in the wrong position, and you have a malunion. That’s the only way that can happen. So, obviously, if you have a stress reaction, you want to get it to calm down. You need to maintain your running fitness while you do that, but you can without turning it into a malunion.
If you want to learn more about this, come check out the Stress Fracture Masterclass. It’s a deep dive into all the things you really need to understand about stress fractures that are unique for runners. It’s about 30 minutes. You can get it for free at docontherun.com/stressfracturemasterclass. And as a bonus, if you sign up there, you’ll get notifications where you can come do a live Q&As whenever I do them. That’s the only way you’re going to get the announcements, but that’s where people can come and ask questions during the masterclass where you have specific questions about your situation, you can ask me there. So again, go to Stress Fracture Masterclass and get it for free, docontherun.com/stressfracturemasterclass. So, sign up and I’ll see you in the training.