#573 How to tell peroneus longus from peroneus brevis - DOC

#573 How to tell peroneus longus from peroneus brevis

Today on the Doc On The Run podcast, we’re talking about how to tell the difference between the peroneus longus and the peroneus tendon when you’re a runner.



If you’ve been running and you started getting some aching pain on the outside of your ankle, well, you might have been told that it was peroneal tendonitis and it could have been a doctor that told you that. You might have figured it out all on your own, looking at some videos or reading about it. But there are two tendons on the outside of the ankle and they do different things and the way that you have to position your foot to reduce the stress and strain on that tendon, if one of them is inflamed, is different because they do different things.

We’re going to talk about that and explain how you can tell the difference between these two tendons. So the first thing is that if we look at your foot and if we draw a picture here and we’re looking at your ankle, so you have the heel bone. The Talus sits on top of the heel bone. The tibia sits on top of that, a shin bone and then you have all this other stuff that you don’t really care that much about, but it’s all in here. That’s more or less your foot.

Now, the fibula, or the bone that you feel on the outside of your ankle, that big lump, that is the fibula bone. So the fibula bone is on the outside, and then you have two tendons. So you have the peroneus brevis. Brevis for short, so it’s the short one so it’s closer to your foot. So you have the peroneus brevis sitting behind the fibula and it comes down, curves around and attaches to this bump on the outside of your foot that we call the styloid process. It’s the base of the fifth metatarsal bone.

When we look at a foot model, you can see here, there’s a bump right on the outside of here and that is where the peroneus brevis tendon attaches. So the brevis is sitting up behind the fibula, comes down around, attach it to that bump right there and what it does is it pulls your foot back under you when you start to roll your ankle over, it’ll pull it back under you and keep you stable. So that’s what the peroneus brevis does. So that one is, as we said, peroneus brevis. Right there.

You have another one that’s longer, which is why we call it the longus. It’s very, very creative. So you have the longus is up above it, still behind the fibula. That tendon comes down and then here, it’s sitting behind the brevis, comes down around and then goes underneath the cuboid bone through a little groove in there, goes across the bottom of your foot to attach to the base of the first metatarsal bone.

Again, the longus is up higher, sitting way up here, up in the leg and then the tendon comes down behind the fibula or curves around the fibula, goes through this little groove right here in the cuboid and then down across the bottom of the foot to attach to the base of the first metatarsal bone. It does something different. It helps keep this bone down against the ground. So when you get ready to push off, the peroneus brevis twists the metatarsal bone, locks it so that you can actually push off and accelerate when you’re running, and that is completely different.

So what are we talking about here? Well, when you look at it from a sort of anatomic perspective, if you look at the foot from the front and these are the metatarsal bones, and this is the ground, and this is your leg, and you’re trying to keep the foot stable, well, the peroneus brevis muscle is the one that basically pulls up on the foot to resist when you have an ankle sprain.

The peroneus longus is the one that actually pulls the first metatarsal bone down against the ground when you’re going to push off. So if you have tenderness in the outside of your ankle, and you’re trying to figure out which one of these two tendons, whether it’s the brevis or the longus, because you want to get it better, we need to know which one it really is.

There’s a couple of simple tests that we do if you come to see somebody like me or your neighborhood podiatrist or a sports medicine orthopedist or any doctor who’s going to look at your foot and ankle and help you figure out how to get back to running. So what is that? Well, it’s really simple.

If you actually take the foot and you cross your legs so that your legs are crossed and you got the little toe joints together, and then you push and you actually apply pressure, that will fire the peroneus brevis tendon and if you watch, you can actually see the muscle starting to flex and you can see it activating. You can see it tense up. You can see the muscle. You can see the tendon curving down around the ankle, around the fibula, where it goes out and attaches to the bottom of the foot, on the outside of the foot, at the base of the fifth metatarsal bone.

That test, if you cross your legs and you push like that, and you have pain on the outside of your ankle, or if you make that muscle fire to make the tendon tight and bowstring under the skin so that you can see it, and then you push on it and it hurts, well, it’s probably the peroneus brevis muscle.

If you’re trying to figure out it’s the longus, there’s another way we do that. What we do is we have you sit in a chair and if you’re sitting down, what I would do is I would sit there with your foot like this. I would literally put my thumb under the ball of the foot, right at the base of the big toe, right where these sesamoid bones are right here and I would tell you, with my thumb right there, I would just tell you, “Push down” and so when I put my thumb under there and you push down, the only way you can push this metatarsal bone down against my thumb is if you fire the peroneus longus. So if you’re firing that, and then I can see that tendon sticking out through the skin, then you palpate it, push on it, manipulate it, squeeze it, whatever you want to call it and it hurts then, then it is probably more likely to be the peroneus longus tendon.

That matters because if you’re trying to get the thing to calm down, you need to not only reduce the inflammation in or around the tendon, but you also need to reduce the stress and strain on the tendon and so if you do something to support the foot in a way that takes stress off the peroneus brevis tendon, well, that will help. But if you’re doing it because you think you have peroneus brevis tendonitis, because that’s just what you thought, based on your reading, but you haven’t tested it to see, and you haven’t really determined which one is which, and you’re doing all this stuff to reduce the stress on the brevis, but it’s really the longus, it’s not going to get better quickly.

Hopefully this will help you understand the way that you can actually test those two individually and then push on the tendon to see whether or not it seems more tender and more problematic when you’re testing the brevis versus the longus. If you understand that, it’ll help you get back to running a whole lot faster.

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