Shin splints in runners: telling the four causes apart

You're listening to the Restoring Human Movement podcast, where movement experts discuss the latest evidence-based practices to help you and your clients move with mastery. Hey everybody, it's Mandy for the Restoring Human Movement podcast. Thank you for joining the Movement Movement. I am your handy-dandy running injury expert. I specialize in working with track, cross-country, road, and especially trail and ultramarathoners. Today we're going to be talking about shin splints. I have a fair amount of experience with this, both as a doctor, a trainer, and personally in my running life. This is actually what got me into the field of sports medicine, since I was experiencing shin splints for three years in high school and NCAA track and cross-country.

And I vowed to figure out what shin splints were and how to treat them, and I have some good information for you guys today. We're going to be going over what shin splints are, and then four kind of subcategories of it and what those look like. For the purposes of this podcast, we're going to define shin splints as pain along the inside of your shin. So just up from your big toe, that aspect of your shin bone. And the shin splints that are on the outside, we'll put a pin in. We'll do a podcast on that later. But that's less common and a different category altogether. So the actual words shin splints just mean shin pain.

So I think it's kind of a crappy diagnosis because it doesn't actually describe anything other than you have pain in your shins, which if you go to a doctor and they say, yes, you have pain in your shins, you're probably going to leave the office saying, yeah, I knew that before I came in. So shin splints doesn't describe much, but the subcategories tell us more about what's going on physiologically. We're going to start off the bat with posterior tibialis tendonitis or tendinopathy. This is one of the first hits on Google. If you look up what are shin splints, and it's something that I thought I had for a long time.

But out of the four categories, this is actually the one that I didn't have. Posterior tibialis tendonitis can be creaky. It can feel like an old wooden door, either towards the inside bottom aspect of your shin, like right above that inside ankle bone, or even down into the foot as well. But it hurts to move your foot and your ankle, even without weight sometimes, and it hurts even more to move that with weight on it. Posterior tibialis tendonitis gets like a super bad rap about it's the cause of everything. It's the cause of all your shin splints. You need to rehab that tendon in order to be healthy, and I actually don't think it's as common as it's made out to be, particularly online.

And we're starting to catch up with the research on, yeah, that's not usually the culprit, but in some cases it can be. So hop test is a decent way to differentiate it from other causes. Hop test is just simply doing like a two-leg hop or a one-leg hop. One leg is even better. We usually start with two legs just in case there's something more serious going on. And if two legs is super painful, you may not want to go to one-leg hop. I use this with my high school cross-country and track athletes, and it's actually fairly sensitive to narrow down the options and send them to the right doctor. But hop test for posterior tibialis tendonitis may produce pain, but it doesn't always produce pain.

If it does, it's likely that the tendonitis is new or recent. And it may be just, again, at the bottom, bottom aspect of the shin or towards your ankle or foot, and it'll feel super sharp and sudden. And then when you're done with the hop, it goes away immediately. That's not to be confused with bone stress injuries, which we will go over at the end here. But typically, hop test is not that painful. And if you're not getting that immediate sharp pain or if you've been having shin splints for a while, you know it's posterior tibialis tendonitis, and you do the hop test, if anything, it's going to be pretty achy and it's going to be pretty mild.

This is much more common in newer runners, especially newer runners or joggers that have been not jogging before and they're going for distance. This is also fairly common in through hikers or people who are hiking for hundreds of miles, particularly with a lot of load on their back. So ultralight through hikers, I'm not talking about y'all mostly. And sometimes I've heard at least that lower drop shoes, like lower stack height and lower heel to toe drop shoes can assist in this. But that's mostly anecdotal. I do know that newer athletes that are doing distance running or jogging and hikers that are going for a long, long hike that have not done that before.

This is more common in them. Next up is medial tibial stress syndrome. You might be seeing it as an abbreviation as MTSS. Now, a syndrome is usually a collection of symptoms rather than a strict physiologic diagnosis. So it's not like saying, OK, you have a broken bone that's telling you what's happening in your physiology that's a specific diagnosis. This is more like I have pain on the inside of my shins. It usually comes on with this. And then they describe it as a syndrome because it happens in enough patients that we need to create a category for it. So for medial tibial stress syndrome, it's described as pain along the medial.

So inside of your shin, usually in the distal or bottom half, usually third of the shin. And it can hurt when you poke it. So usually when it hurts when you poke it, you can help differentiate between the subcategories based on how much it hurts and how wide the area is of tenderness. So for MTSS, usually if you poke it, the pain is in a pretty broad area and it's not that severe. So it's not like you poke it and you're like, oh, crap, I got to not do that. But it's just kind of achy and tender along a broad area. This can be chronic and it's kind of a low-level irritation. A lot of doctors actually use MTSS synonymously with shin splints.

So sometimes you might be diagnosed with MTSS and it not be MTSS. But for a lot of folks, they just assume that shin splints is the same thing as MTSS and vice versa. There are theories as to why this happens, but there's no conclusion, at least that I know of. And I've done some research searching and there's no strict conclusion on why MTSS happens or why it can be so chronic. But some of the leading theories have to do with where the muscles in your lower leg attach to the bone or the tibia. And the theory is that these muscles pull on the bone and it can create a bending force that irritates where they attach at both ends of the muscle.

Or they can start irritating the periosteum, which is the covering of the bone. Think like a sausage has that casing around it. That's basically the periosteum is the casing and the sausage is the bone. Again, MTSS can be pretty chronic. I would actually say that I have MTSS now, even though I don't have any symptoms when I'm running or doing anything. But if you poke the last third of my shins on either side, it's going to hurt. So I have no symptoms when I'm being active at all, even though some folks do have symptoms and they have MTSS. But for folks who just have been running for like, say, 20 years, and if you poke their bottom shins, it hurts.

Yeah, they may technically have MTSS, but it may not be relevant in their daily life. The hop test, again, like two leg or one leg hopping, doesn't usually elicit pain. And it may in some cases be a very dull ache, but it usually is not like a sharp, oh crap, I have to get off my feet type of pain. If you do have that, you're probably in a different category. But again, poking the shin, it can be tender, but we're talking more broad area. And there's no specific spot that's really sharp. So again, last half of the shin bone, maybe last third. If you poke it and it's low-level tender all along the bone, you've ruled out other diagnoses, likely we're talking about MTSS here.

MTSS does have some overlapping characteristics to periostitis, which is our next subcategory. And again, just a reminder, the periosteum is the sausage casing that lies around the bone. In my head, there's actually two subcategories of periostitis, and the first being the one that is synonymous with MTSS, where it's an irritation of that sausage casing. And it hurts when you poke it, and it's a pretty broad area, and it's not associated with anything else like a bone stress injury. This, again, could be due to where the muscles attach, which again, that's why it's included with MTSS a lot of the time.

So if it shows up on an MRI, it's usually this kind of bright white area that's diffuse. It covers a fairly broad area. And again, there's no bone stress injury associated with it. It's just that sausage covering. And this is why it can be pretty tender when you poke at it. Compared to broad MTSS, usually periostitis is a smaller area, but still fairly diffuse area of pain when you poke at it. But the important part of periostitis is to rule whether it's part of MTSS or whether it's part of a bone stress injury. Now, everybody's favorite category, we're going to talk about bone stress injuries.

And this is usually described as stress fractures or stress reactions. Stress fractures are where there's actually a crack in the bone. Stress reactions are usually a precursor to stress fractures, but the fracture line hasn't developed yet. So it's usually swelling or edema in the bone itself. Stress reactions and stress fractures can have periosteal reactions. So periosteal reactions are swelling in the periosteum. This is why it's that second subcategory of periostitis. And it can show that it's a precursor to a stress reaction or a stress fracture or it's happening at the same time. So if you do see this on imaging, it's important to figure out why it's there.

For bone stress injuries, they are generally a more severe pain and they generally come on fairly quickly. So you may have low-level shin splints for a while, shin pain for a while, but usually there's a course of a couple days or a week where it starts getting worse and worse and worse and all of a sudden you're like, crap, this is, I got to deal with this immediately. Stress reactions are technically less serious than a stress fracture, but in reality, you treat them the same way and you treat them with rest. And this may not even be relative rest where you can do other things during it. It may be absolute rest, at least for the first few weeks.

But we're talking on the order of 6 to 12 weeks of rest total. These are described more as severe pain or throbbing even, and it can happen at rest. So for those of you who are laying in bed at the end of the night and you notice that your shins are hurting and you were running earlier that day and it was really bad and you were limping, that's when you should be suspicious of something more serious like a bone stress injury is happening down there. It can be tender in a broad area, just like our other categories, but usually there's an area where it's worst. Even in a stress reaction, there's usually a focal point where it's coming from.

And obviously in a stress fracture, if you're able to poke the fracture itself, it's going to hurt like hell. Sometimes people don't think that they have a stress fracture because they can't find the one area where it hurts, but that doesn't necessarily rule it out, in part because you can have a stress fracture on the back of the tibia. So that's more like where your calf muscles are and you can't actually reach that part very easily. That was exactly the case when I had a stress fracture. I didn't know it and I had had shin splints for three years leading up to it, which in reality were probably MTSS to start and then periostitis and then ended up being a stress fracture later on.

But I couldn't poke the area, so I thought I was still in like a periostitis or MTSS situation. In reality, I was just thinking, okay, I have shin splints and all of a sudden I couldn't really run without limping. I ended up running on it for three or four weeks, just way lower mileage. So take it with a grain of salt that it's severe pain. It's not always that severe and it can go unnoticed until finally you get an image and you see the fracture line or the periosteal reaction or the edema in the bone itself. A hop test is fairly sensitive for this and again, you start with double leg hop and you can move to single leg hop if double leg hop is no big deal.

But the single leg hop, yes, obviously it can hurt, but also you should be looking for apprehension. So I recently had a patient actually with, it ended up being a confirmed stress fracture in her tibia and she was hopping on her left leg, which was fine, just fine. And then when we went to her right leg, she almost couldn't hop, like there was no power behind it. And she said it actually didn't hurt at all. She had been having symptoms for a few weeks before that. She was trying to hop and it didn't actually hurt, but she just couldn't do it. It's like her brain was stopping her from doing it.

If you're seeing that apprehension, that should also be a sign that you need to go get an image or you need to go to the doctor and explore if it's a bone stress injury or not. She got an MRI, I think a week later, and it was confirmed as a stress fracture in the tibia. So all this to say, shin splints is, again, kind of a crappy diagnosis. If you just think, oh, I have shin splints, you may want to dig deeper, especially if you're concerned about a bone stress injury. And if you have, I'm going to beat you guys over the head with it, REDS, relative energy deficiency in sport, or osteoporosis or osteopenia.

If there's any reason to suspect that your bone density may be low, this is where it's more important to get into a doctor and see what it could be. Again, shameless plug, I'm a real person, not somebody who just speaks at a microphone all day. I treat runners, so if you're interested in coming in and getting an assessment done, see my information in the description. But not to scare y'all or fear monger, if you're suspecting a bone stress injury and you don't deal with it, it can fracture fully and it can, like, break your entire shin bone. There was somebody I saw in college, and this is horrible, this is kind of the worst-case situation.

He was running a race, it was actually one of the last cross-country races of the season. He was running on a stress fracture, and actually the coach knew it was a stress fracture and kept him running, which is awful. But he was running on a stress fracture, it must have been his senior year or something like that. And in the middle of the race, he took a step down and his entire shin broke, like broke through, not just the fracture. So, again, important to rule out if it is a bone stress injury or not. We don't want to be like that guy who had to take the VIP golf cart ride back to the start line and then went to the hospital, obviously, right after.

I will say there is a bonus category that I find is more common than any of these in people who have had it for a long time and don't have tenderness along the bone. The bonus category is a lumbar referred pain or a nerve pain down there. We've gone over this extensively in other podcasts, but just as a reminder, nerve pain doesn't have to be sharpened shooting. It can be any type of sensation, including numbness and tingling, but it can be achy or sore or dull pain as well. I find this to be fairly common. So it is important to get an assessment with somebody who knows what that is and the possibilities, even though, say, it's a lumbar referred pain.

You may not have pain in your back or your sciatic nerve or anything like that. It may just be in your shins. So, again, check out our other podcasts for information on that. We will do a podcast on that specifically because there's some different signs and symptoms of that. But if you've gone through all of these diagnoses and you're not finding anything and your shin splints aren't getting better, it's not getting better with rest, especially. You should be suspicious of a possible nerve issue, and that requires much more specialization in your treatment. Thankfully for the nerve stuff, it's fairly easy and quick to treat if you know what you're looking for.

But most people don't know what they're looking for because it's shin splints, right? You don't think nerve off the bat. So if that is the case for you, you've been dealing with this for many years, it's not tender along the bone, reach out to us. We know all of these categories so we can assess for which one you have. And in the meantime, check out our other podcasts. We have a ton. We also have a YouTube channel with some information on shin splints and other running injuries. And if nothing else, just shoot us an email with your experience. We always like hearing people's different experiences to broaden our knowledge base as well.

And we may be able to point you in the right direction.