#629 Cuboid stress fracture vs. Degenerative changes in OS Peroneum. How can a runner tell the difference? - DOC

#629 Cuboid stress fracture vs. Degenerative changes in OS Peroneum. How can a runner tell the difference?

Now, if you’re a runner and you have an aching pain on the outside of your foot, just in front of your ankle, you might think you have a cuboid stress fracture. If you’ve had an x-ray that shows you have a tiny little extra bone sitting there over the cuboid, well that’s a thing called an OS peroneum and sometimes you can get pain from the OS peroneum, sometimes you can get pain from the cuboid bone that’s right next to it. If you’re a runner and you have that pain, how do you tell the difference? Well, that’s what we’re talking about today on the Doc On The Run podcast.

In this episode we’re talking about two bones in your foot that could cause pain, and particularly the cuboid bone. When you’re worried you have a cuboid stress fracture, first of all, that’s really rare, but getting pain from this thing called an OS peroneum, which is a different little bone sitting right next to the cuboid, that’s also very rare as well.

How rare? Well, cuboid stress fractures, there was a study of 117 soldiers who had stress fractures in their feet and only one of them was from the cuboid. Most are from the metatarsals, which are way more common. But I think it’s going to be helpful to draw some pictures and show you what we’re talking about here. If we look at your foot from the top, the front of the heel bone actually sits over here like that, and then you have the cuboid.

The cuboid bone lines up with the fifth metatarsal bone, and you can always find that because there’s a bump that sticks out on the side of your foot where the fifth metatarsal bone sticks out. Right there you’re close to the cuboid. You can’t really see the cuboid, but if you can find that bump, you can find the cuboid.

Then you also have the fourth metatarsal bone, which lines up with the cuboid and sometimes you have a little bitty bone sitting right here. What is that? Well, that’s the OS peroneum. An OS peroneum is an accessory bone. Not everybody has it, but sometimes it forms and it sits over there and it can cause some trouble. If we look at your heel bone, this is the front part of the heel bone where the cuboid lines up. The cuboid is here and fifth metatarsal bone is here like that, and then the fourth metatarsal bone is over here like that.

The OS peroneum is actually embedded within the peroneus longus tendon. The peroneus longus tendon actually comes down, muscle’s way up here, and the tendon goes from the muscle, down around your fibula bone on the outside, and then it curves your little groove in your cuboid bone and so it goes right around that groove and it goes across the bottom of your foot to attach to the bottom of the first metatarsal.

It wraps all the way around the foot so it’s going across here underneath the cuboid after it wraps around right there. But right here, that OS peroneum, it’s actually embedded in the tendon itself so it’s not just hanging out there, it’s not floating there, it’s attached to stuff, and what it’s attached to is that tendon. The OS peroneum, sometimes you can see it on an X-ray, again, not everybody has it, but they’re two different things.

A couple of the reasons you get pain in this area. If you have pain on the outside of your foot here or here, well, one reason could be that you have have inflammation within this bone, the cuboid bone. And the cuboid bone is really inflamed and irritated and that’s why you have pain. That could be a stress fracture. If you get a stress fracture, the bone is basically swelling on the inside and if you keep it swollen, that increased blood flow that’s causing that swelling decreases the bone density and then it eventually forms a real crack that we call a true stress fracture. You do not want that obviously.

Now, the good thing is that that blood flow to that bone is really good so it can heal really quickly if you leave it alone and stop stressing it. Now, that’s the key indicator here. The thing is, is that looking at you and poking around on your foot or you testing it yourself, it’s very, very difficult for you to tell yourself, is that pain because of the cuboid or the OS peroneum? Because if you push real hard right here against the cuboid, it’s going to hurt if you have a stress fracture in the cuboid. It’s also going to hurt if you have a painful OS peroneum that’s inflamed and irritated and starting to degenerate. It doesn’t really help to do your own physical diagnosis that much. If you’re able to push on the cuboid and not push on the OS peroneum and you’re able to push from the top or making sure that you’re not on the peroneus longus tendon at all, then you certainly can do that and you can discern that way.

If I were looking at you, I’d probably be able to do that. And if you called me on a webcam visit, I’d have you look at your foot, I’d have you draw some stuff on your foot and I’d tell you what to push on and what not to push on so that you could tell the difference between those two things. But it’s hard to do on physical diagnosis to really make the call and first of all, if you haven’t had x-rays, you don’t even know if you have one of these little bones called the OS peroneum. If we got x-rays, we’d be able to see at least, do you have that bone or not? And so I could order x-rays for you and we could look at those on screen share and figure out whether or not you even have that bone. But that’s the first thing.

Again, even if you could feel a little lump in the tendon that might be the OS peroneum, it could also be tendinosis. If you haven’t had an x-ray, you can’t tell. An MRI is more helpful. An MRI is really helpful because if you have this inflammation within the cuboid bone that is indicative of a stress fracture, it will show up on the MRI. Also, if you do not have that inflammation within the cuboid bone, you know you don’t have a stress fracture of the cuboid. And if instead you have selective inflammation formed all around that OS peroneum embedded within that tendon, well then you know that that’s really your issue is that it’s inflammation of the peroneus longus tendon and the OS peroneum that’s embedded within the tendon. Different problems, different treatments so you’ve got to really know what the difference is.

If you can’t figure it out yourself, you got to talk to somebody, get a second opinion. If you go see your doctor, your doctor could do x-rays, your doctor could look at you and poke around and help you try to figure this out. If you don’t have access to your doctor or you can’t see them any time soon, you could do a webcam visit with somebody like me so that we can actually figure out what’s going on, order the x-rays for you, take a look at the x-rays with you, and if necessary, even order that MRI.

But don’t ignore it. Again, the cuboid, if it’s a stress fracture, will heal very, very quickly if you do the right stuff. If you do not do the right stuff though, it can definitely get worse. You want to make sure that you’re reducing the stress on the injured structure, but if you don’t know which structure it is, it’s hard to figure out what to do. Now, if you like this episode, please share it, please subscribe and I’ll see you in the next training.