Hoffa's Fat Pad Impingement: Outside Knee Pain in Runners

You're listening to the Restoring Human Movement podcast, and now your host. Hi all, welcome to the Restoring Human Movement podcast. Thank you for joining the Movement Movement. This is Dr. Mandy. I am your handy-dandy running injury expert, and today we're going to be talking about an injury I've actually been dealing with for a little over a year now. Super quick background on me for those of you who haven't heard my voice on podcast or seen me one-on-one. I did NCAA cross-country and track. I ran cross-country and track in high school. I now coached cross-country and track as well, but my main thing now is trail running, ultra running, and trail races in general, even if they're sub-ultra.

So that is my main jam now. I've done quite a bit of it, and I mainly treat trail and ultra athletes, but really distance runners of any kind. So on to this injury I've been experiencing for the last year. This is called Hoffa's fat pad impingement. What it feels like, it's outside lower knee pain, but it's not obvious knee pain. It's not like, oh, I touched my kneecap, my patella, and it hurt. I didn't tear my ACL. There wasn't a moment where I planted and twisted in a spore and I felt it pop. There's actually no popping and clicking overall, and no bruising. I actually wouldn't say that there was a true mechanism of injury, like there wasn't a specific moment where I did something to my knee and I was like, oh, no, now it's injured.

It just came on fairly gradually, but there was one run where I was going down a pretty steep descent, and there were very short switchbacks where I was turning a lot, but it was mostly the descent. It was a little bit loose and rocky. And after that, I started feeling it a little bit. Now, granted, I also stood at a track meet coaching my athletes for about 12 hours afterwards, so that may have contributed. But since then, it's been a just very low-level, achy knee pain that I feel mostly on downhills, no problem uphill. I sometimes feel it in my squats when I lift and occasionally in my deadlifts as well, despite it being a pure hinge.

And I've kind of been ignoring it, frankly. I am my own worst patient in that I'm like, oh, just, you know, it'll get better on its own. And I actually, this started last year in April, and I had a big target race. I did Kuyamaka 100K in October. It was my first 100K, so it's not like I was going to stop training, and I think a lot of us can relate to that. Plus, it wasn't really that painful. So, did the 100K, went well, if hot. And afterwards, I took usual rest. I usually take at least a couple weeks completely off, started running a little bit, and really kept it very low mileage after that.

But the knee pain kind of stuck around. And again, it didn't really get worse. I actually didn't really feel it in the race. Also, you know, there were just other things that were hurting in an appropriate fashion that kind of took my mind away from it. But even then, I didn't feel it at the start. And once I got back into running, it was still kind of there, which proved to me that rest didn't really help it. And if it was going to help it, it probably would have helped at the beginning of the pain, rather than once it's become chronic and, you know, I've been running on it for months, that rest didn't really have much of an effect.

The anatomy of the anatomy of this injury is fairly interesting. So if you find your kneecap and you feel down your kneecap to your patellar tendon, that's the tendon that goes from your kneecap to the top of your shin, and you go just to the outside of it, you're going to feel a divot there. It feels like there's not really anything there. Deep in there is Hoffa's fat pad. I don't know who Hoffa was, but that's the name of it. And that fat pad is basically used to reduce friction between the femoral condyle. So that's kind of the bump, one of the bumps of the end of your femur and the kneecap.

So how this fat pad impingement comes around, impingement means pinching, which means either the fat pad is swollen and therefore taking up more space and getting pinched more easily, or your femoral condyle, the lateral femoral condyle, the one to the outside, is actually bigger than normal. It's more prominent, or both. You can have a prominent femoral condyle and swollen fat pad, and then you're really pinching it very often. I mostly am in the big femoral condyle, lateral condyle boat, but it did show on MRI that there was a little bit of swelling in the fat pad itself. That being said, it wasn't obvious swelling.

Like, I didn't look at my knee and go, oh my god, it's the size of a basketball. It showed a little bit of edema, which means it was getting pinched and irritated. But again, I just got this MRI a couple weeks ago. So this is 13, 14 months after I started feeling it. So it actually didn't show any damage, which was comforting to me. I actually got the MRI to make sure that there wasn't any true damage. Like, I didn't rupture anything. I didn't tear anything. I wasn't going to screw it up by keeping training through it. And it just showed that little bit of swelling, and it proved that my lateral femoral condyle is quite big.

It's very pointy, especially compared to the medial condyle on the other side. And here's where we get into the ever-controversial patellar tracking. So tracking is basically how your patella, your kneecap, moves throughout the groove between each femoral condyle. So if you've ever seen a chicken bone and you see those two bumps at the bottom, those are the condyles of whatever bone you're looking at. And in between those two condyles is where the patella sits, and it can slide, ideally, forward and backwards, such that when your knee extends and flexes, that's nice and smooth and there's no clunking.

Your patella doesn't really, like, run over any bone structures. And one of the things that helps it is, on the lateral side, is the fat pad. It reduces friction. But there's other structures, like bursa and, like, cartilage under there, and things that help it slide and track in that groove and stay in that groove when you're doing anything with your knee. So there is controversy about patellar tracking, saying that it can get off-center and kind of rub on one of those condyles. It's been proven to be relevant in a lot of injuries, although it was kind of the smoking gun for a lot more injuries than we found out recently that are actually, like, not involved with patellar tracking.

But this is one case where patellar tracking can be relevant, because if you have that large lateral femoral condyle, that large bump on your bone on the outside, and your kneecap isn't sitting in that groove in between the condyles very well, like, when you flex it or extend it, it kind of moves to the outside rather than moving straight in that groove, it can rub on the fat pad and kind of impinge it or pinch it, and that can create some swelling into this lovely cycle of fat pad swells a little bit, now it's easier to pinch, it swells a little bit more, now it's even easier to pinch, and so on and so forth.

There is quite a large range of how symptomatic you're going to be. So for me, I got fairly lucky. It really only hurts if I totally extend my knee and squeeze my quad, and sometimes I can feel it on the downhill again. Some people, it really hurts to stand on it, and it is a lot more swollen. Maybe it's even creaky. That happens when the swelling in there, it kind of creaks. It feels like an old wooden door. It's called crepitus. And for others, it's not even a problem, and they never notice it, and since it's not really an injury that immediately causes damage, it's no big deal. Now, again, I ran straight through it. If you've seen me in person, you know that I really hate sitting athletes.

I think a lot of time, rest doesn't work, especially if we're talking about a chronic case. And I had 100K coming up. I wasn't going to sit unless my leg was falling off, honestly. But here's some things that I wish I had done earlier, because again, I'm still feeling this, and now I'm starting to take care of it because of its chronicity. It's probably going to take longer than if I had just dealt with it in the start. Number one, this is one of the only injuries I actually recommend icing for. And that's in part because the actual problem is the swelling. Now, if you have a big lateral femoral condyle, you can't do anything about that condyle.

It's not going to change because it's a bone, unless you go get surgery. But usually this is not a surgical intervention type of injury. So icing can help bring that swelling down. But remember, with icing, at least in my opinion, I think it's only useful as long as it's useful. So if you ice and you find out, like, okay, I don't feel any better, it doesn't seem to be helping, don't use it. And if you do ice and you realize, oh, it does feel really good afterwards and it lasts throughout the day, actually, not just the moment where it's numb because of the ice, I'd say go for it in this injury until it runs out of usefulness.

So at some point, maybe a few days, a couple weeks in, you're going to notice that you're going to ice it and it's not going to make a difference. Or you've just started icing it and now you think it's something you have to do. At some point, blood flow through the area is going to be important to bring the crap out of it. By crap, I mostly mean inflammation or dead parts of tissue. You need things in your blood. They're kind of like trash men where they go and they transport to the area that's injured. They load up the trash, which is, again, like dead tissue or inflammation. And then they carry it out into your lymphatic system and suddenly it's less swollen.

Those are important. So you do need blood flow to get to that area in order for the trash men to get there. But in the meantime, ice can bring down swelling some. And if we're talking about something that's getting pinched because it's swollen, it can be useful. Now, talking about ice, what might come to mind is RICE, R-I-C-E. That's the old, actually, acronym that is used for injuries and how to recover from it. PRICE is also a slightly updated version. And now there's a whole new acronym called Peace and Love. So PRICE, we'll go in the middle here. PRICE is Protection, Rest, Ice, Compression, Elevation.

Not all of these are going to be relevant for this injury. And actually, I would argue that compression would be inflammatory for it and potentially make it worse. But protection, probably not important. Protection is mostly like if you have a, say, like an ACL tear, you don't want to get hit in the knee again, right? So you have this huge brace on that somebody accidentally bumps you in the knee. It's no big problem. Rest, I would argue, would be useful in the early stages of this. It might even be useful in the later stages. I frankly haven't trialed it. And I don't usually have my patients trial it because, well, one, I and my patients want to keep running and they want to keep doing the activity.

And I can virtually guarantee anything less than a bone break or my leg is falling off. And I told you, hey, take eight weeks off. You would just go find somebody who tells you not to do that. But honestly, a little bit of rest might help. But if it doesn't help, don't keep doing it. If it doesn't help the first time, it's probably not going to help the second or third time unless it gets drastically worse. Ice, we've already covered, can be useful, can not. Compression, I would not do. There's actually great taping techniques out there on how to offload the Hoffa's fat pad. You can look up Hoffa fat pad taping or McConnell taping.

I would try them out and see if they help. But I would be wary against kinesio taping, so K-tape taping. It doesn't seem to have enough force to really influence much. Y'all might have different opinions on it. If you find that this is useful, actually, for Hoffa's fat pad impingement, please send us an email. Because in my experience, I haven't found it that useful. But also, I default to a different type of taping for this. So if you disagree with me and you think that K-tape is useful for this, please send us an email and tell me about your experience here. And lastly, in price, we have elevation.

Elevation is great for things that are really, really swollen. So we're talking ankles that look like the size of a softball all of a sudden. They're not as useful for things that aren't super swollen. So elevation, the thought is, your blood flow is helping bring things down through gravity and take the crap out easier. So I don't know if this really affects how many so-called trash men get to the area. But it seems to help speed up the process of that swelling naturally moving up towards bigger lymph nodes, usually found in your groin area or your hips, and helping bring that swelling out. For this, I don't think it's super relevant unless you are on the severe side of this, where it is obviously swollen.

But for most people, I don't think it's that useful. All this to say, to kind of sum it up here, Hoffa's fat pad impingement, it's on the outside part of your knee, kind of in that gully between your patellar tendon and the outside of your knee. It can be mildly painful, or it can be very painful. Most people are in the mild to moderate range. And it's not actually damaged most of the time. Like, you usually didn't tear anything unless you leave it forever. And then, yes, the fat pad may start to calcify or start to fray a bit. But for most of us, it's not damaged. But it is useful to hop on it, in part because the more chronic it gets, the harder it is to heal itself.

But my one big tip, other than maybe some ice, some topical NSAIDs, actually, like Voltaren can help as well. My one big tip is you need to offload the area. So if you're using your knees a lot, like us trail runners do, running downhill is essentially a squat over and over and over. You need to offload the knee temporarily. And that can mean keeping running, but really, really hammering your hinge patterns. So we're talking deadlifts, ideally fairly heavy deadlifts, as much as you can go without putting the rest of your body in danger or pissing off the knee. But hinge patterns help offload the knee and move work into your hips, which have much bigger muscles and are able to tolerate that workload better.

So that means that when you are doing whatever hurts the fat pad, the force and the movement may come from your hips more than your knees, which can help not pinch that fat pad so much. I have been hammering deadlifts since my race in October. After I took those couple weeks off, I really got back into strength training, like focus strength training. And it has helped. And I would attribute the lack of it getting worse to me really hammering my hinge patterns again. You don't get a ton of hinge patterning in trail running. It depends on the person, whether you're quad dominant or hinge dominant or torso dominant, but most people don't get a ton.

So putting this in your strength training program is crucial and not only can help avoid being in the situation in the first place, but it can also help once you're in it. The hard part is figuring out how to implement some of this stuff without guidance. It's really easy to piss it off again if you're not doing exactly the right thing because of how specific the biomechanics of the actual problem is. So if you need help, again, I'm not just somebody who talks at a microphone all day. I am a practitioner. I am a doctor of chiropractic and certified medical exercise specialist. Work with people in person and virtually.

So reach out. Even if you just have some questions about what's going on, reach out to us. All the information is in the description. Till next time.