Bone Stress Injuries (BSIs) are frustrating and confusing. Understanding how BSIs heal is vital to allow us to return to running. This video highlights critical concepts you need to know and how to progress back to training. Here are a few topics I cover.
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You’ve been diagnosed with a stress fracture. How’s that thing actually going to heal? That’s what we’re going to go through today.
When we develop a bone stress injury, what happens is there’s an imbalance between the damage that occurs and our body’s ability to remove that damage. Then we begin to experience some pain, and eventually we get an image that says that we have a stress fracture. What’s the process that our body goes through to heal that stress fracture, and what can we do to make sure that we heal it to the best of our abilities? There’s two different processes that work together to allow our body to heal a stress fracture. The first one is called targeted remodeling. This happens through two different cells, our osteoblast and our osteoclast. Our osteoclast break down the bone that has been damaged. And then our osteoblasts come in and they heal that over time. This breaking down and then replacing with new bone happens over and over and over again, and it happens on a very specific level.
Now to envision this, let’s zoom in on the fracture. We can envision the osteoblast and osteoclast acting like a small tube of superglue. Very, very precisely, it’s going to go and it’s going to fill in the specific injury site, it’s going to make it super solid, but it’s going to take some time to make sure we don’t have superglue all over everything. Now, we have a second process that helps with this, and that’s called global remodeling. It’s a bigger process that’s less specific. I want you to imagine I have some putty and I’m going to fill in this crack, but I’m not going to take my time. I just want this thing over with, I’m going to slap some putty down. It’s going to heal. And then eventually over time, it’ll get back to its normal formation. These two processes work together, very specific remodeling, and then more global remodeling that happens in a much quicker fashion.
This global remodeling, because it’s faster, because it’s not as specific, is part of the reasons why sometimes people will say, “Well, I had a stress fracture right here, and I still have a bump there.” That’s a normal thing. One of the downsides about global remodeling is that it is affected to a greater degree by our hormones. With many bone stress injuries, hormones are a component of why that injury happened in the first place. So if our hormonal function is not exactly where we want it to be, it could affect how that bone is going to heal from a global standpoint. All right, so that’s a general process for how this happens. But how long is this going to take, because all I want to do is get back to running? We have two types of bone in our body. We have cortical bone and we have cancellous bone.
Cortical bone is more present at the end of long bones. It’s more sturdy in nature. Cancellous bone, or spongy bone, is more present in our spine, in our pelvis and in the proximal aspect of our hips. It’s important to designate these types of bone because we get stress fractures in both of these bone types and they heal at different rates. We categorize bone stress injuries into high, medium, and low risk. A big reason why we do that is because different bones are made up of different percentages of cortical and cancellous bone. Bones that are more cancellous or spongy in nature are generally higher risk because they have a harder time healing, they take longer, and often, there’s more things that have gone into why that injury happened in the first place.
Injuries to cortical bone tend to heal a lot quicker. That’s why someone with a metatarsal stress fracture or a stress fracture of their tibia tends to get back to running quicker than someone that has a sacral stress fracture or a femoral neck stress fracture. Cortical bone, we can return to running quicker. Spongy bone, we have to take a longer time. It takes between four weeks to three months for our cortical bone to completely turn over. That’s a lot different than spongy bone. Spongy bone can take around 200 days to completely turn over and recover. This is why when you walk into your doctor’s office and they tell you that you can run at four weeks after an injury, it’s not necessarily the most helpful information. There’s a lot that needs to happen before we can say, let’s start running again.
To get diagnosed with a stress fracture, you’re going to have to have an image. Normally, this is an MRI. On that MRI they’re going to tell us the location of the stress fracture and they’re going to grade it. There’s a few different ways to grade stress fractures. This table is helpful here. If we have a stress fracture that is a higher grade, it’s going to take longer for that bone to heal. If we have a stress fracture that is a lower grade, we’re going to be able to return to running quicker. The grade of the image is going to affect when we can return to running. The bone that’s affected is going to affect when we can return to running. We see that low risk bone stress injuries tend to return to running at about 13 weeks after an injury. When we look at those high risk sites, we see that it tends to be about 24 weeks to return to running. That’s how stress fractures heal, and those are the general timeframes to return to running.
But there’s another big variable that plays into this, that I’ve talked about in my videos before. The athlete triad and the bigger issue of relative energy deficiency in sport is a common variable in why these happen, and a roadblock into getting back into running. When we have low energy availability, we see that it can take days to weeks for us to return that energy status to normal. When we look at our hormone function, we see that it can take weeks to months to restore. Finally, when we look at our bone mineral density, we see that it can take years for that to completely return to normal. Sometimes our bone mineral density is worse after an injury like this.
When [Poppen 00:05:13] colleagues followed runners following a tibial stress fracture for a year, they saw that 33% of the runners did not have their full bone mineral density that they had before their injury. And this is a big reason why I think the rehab from a stress fracture should often parallel the rehab for an ACL reconstruction. When someone has an ACL reconstruction, it’s very common for them to wait nine to 12 months to return to their full sport participation. I think we should have a similar timeframe for most of our stress fractures. And the reason is because if it takes the body that long to completely recover from one of these, and if we’re having to have some kind of changes in our nutritional strategy, in our relationship with exercise, and in our hormone function, that’s going to take a lot longer than a few weeks to completely work itself out.
Now, this isn’t to say we need to keep runners from running for many months after one of these. It’s to say, when we do start running, we should start really, really slow. And it should take a very long time for you to return to your previous level of competition. Practically, what this means for me, we’re not going to run back-to-back days for multiple months, when we can run. That 24 hours allows our body a chance to recover from that bout of running and allows us to assess how the session went. Now, once we get to the point that we’re running a significant amount, I’m only going to change things in two week intervals. So the first time we can start doing any kind of intensity, we’re going to add in strides. And the only type of intensity that you’re going to have is going to be strides, for multiple weeks.
And when we’ve graduated from strides, we’re going to go to a tempo run. And that tempo run’s going to be very short in nature. Over time, it’s going to increase, and we’re going to do that for multiple weeks. And then after you’ve done that, we’re going to add in intervals. And those intervals, again, are going to start very short. There’s never going to be a point where we just say, “Boom, back to normal training.” It’s going to be a very slow build. So when we’re going through one of these, it’s important that we have a team approach where there is a physician, a rehab specialist, a coach, and the athlete. We are all coming together, hands-in in the middle saying, “We’re all on the same page.”
If we take that slow approach, if we take that team approach, and if we have that broad rehab plan, I think we can knock most of these out of the park. I hope you found this video helpful. Let me know if you have any questions, and have a great rest of your day.