What is the difference between fat pad atrophy and fat pad displacement in runners? Well, that is what we’re talking about today on the Doc On The Run Podcast.
If you have a pain in the ball of the foot, underneath the bases of the toes, that is right where your fat pad cushioning is. Sometimes you can get the pain because you have a neuroma. Sometimes you can get that pain because you have a plantar plate injury. Sometimes you get that pain because you have irritation of the joint capsule or sometimes you have this thing called metatarsalgia, which is a term I am not crazy about, but it basically means you have aching in those bones at the ball of the foot and oftentimes it is because you have this thing called fat pad atrophy.
I think there is a lot of misunderstanding about what fat pad atrophy really is, particularly when it is related to something like a plantar plate injury. Sometimes people have true atrophy, but that is rare. Sometimes people have displacement and I think that is more common and I am going to try to explain why.
Again, I am a podiatrist. I am not an artist. I’m going to do my best, but don’t expect great pictures here. But here’s the thing. So, if we look at your foot and let’s make it exaggerated. So, you got a high arched foot and that is the toe. You’ve got the fat pad cushioning that is under the ball of the foot. And so, we’re going to get to this in just a second, try to explain it here. See if I can make this a little more clear than it may be at the present time. And my terrible drawings may or may not help, not sure which, but feel free to post in the comment about how terrible it is.
Okay, so let’s talk about this. So, let’s say you have atrophy. Atrophy is where the fat pad gets thinner. It is where it gets smaller. So, if you have atrophy, what happens exactly with the ball of the foot? If you think about atrophy, it is where the fat pad, let’s say you’ve got to make it a clear illustration, you have, let’s say two rows of thick globules of fat, like marbles. That is not really how it works, but it is sort of how it works.
If you had atrophy, those things would all get considerably thinner. So, they’re still there, but they’re thinner. And what is underneath there? Well, it is the metatarsal bones, right? You have the metatarsal bones, proximal phalanx, intermediate phalanx, and distal phalanx bones sitting in there. If you have that here, what does that translate into? Well, it is really simple. When you have fat pad atrophy, there’s less material between the bone and the skin to cause cushioning. When you have the fat pad atrophy, what that translates to is a lot more pressure under this area when you stand up.
Fat pad displacement is different. Fat pad displacement is where you’ve got, let’s say we put the four same seven globules in there. You have the same amount of fat, but it is moved because the toe has changed direction. So, if you have the plantar plate here like this, you’ve got the plantar plate that holds the toe down against the ground. But let’s say in this case, it ruptured. So, you have an actual tear in the plantar plate here. It is no longer connected. That allows the toe to drift upward.
When the toe drifts upward, after you have had something like a plantar plate sprain, or you have rheumatoid arthritis, and you get hammer toes, or for whatever reason, you get deformities that let your toe drift up and develop a hammer toe, that really changes things because you still have the metatarsal bone sitting where it is supposed to sit, but the ligament is torn. And now the toe is crooked, right? It is completely jacked up, sitting in a different position, and you have a hammer toe.
The ligament that is torn has done something very interesting. What it does, because the fat pad is anchored in the toe, then what you have is the same amount of fat, but it is in a different position. It has now moved from here, up there. And because it is sitting up here when it was down there, that allows a huge amount of pressure to happen right under the metatarsal bones, because now you have no cushioning at all in this area and that is a totally different thing. That is fat pad displacement.
Displacement because it is in the wrong place. It is displaced. It is not where it is supposed to be and that causes a bigger problem. So, when somebody says they’ve had a plantar plate injury and they think they have fat pad atrophy, number one, you can’t really tell for sure unless you have some previous kind of measurement, like an ultrasound that measures the thickness of the tissue before and after. Maybe it has always been that thin.
There’s a reason you could get atrophy and that would be from a corticosteroid injection. That does happen. There are other metabolic disorders and some diseases that we know have disease processes associated with atrophy or thinning of the fat pad but most of the runners I see who are young and healthy and active in their thirties, forties and fifties, it is not really atrophy. Many times it is just displacement.
The fat pad has been moved up out of the way and in the wrong position. And now you’re getting pain because you don’t have enough cushioning there. So, look at your foot. See if you think you’ve had any change in position of the toes. See if the fat pad, if you still have it and it is sitting up here under the basis of the toes, just not under the ground where it is supposed to be. That is different.
If you want to learn more about the strategies I use with runners who have plantar plate injuries, and they’re trying to get back to running, trying to keep training, all of that, I go into a deep dive on those strategies specifically in the plantar plate masterclass. You can get it for free www.docontherun.com/plantarplatemasterclass. So, thanks for watching and I’ll see you in the next training.
