Episode 94 | Is Numbness Normal after ACL Surgery? Part 2

What is up guys? Welcome back to the ACL Athlete Podcast. Today is episode 94. We are continuing the two-part series, answering the question: Is numbness normal after ACL surgery? Today is part two and we are building off part one. If you are listening to this and you have not listened to part one, stop everything you’re doing stop this episode and go and listen to part one. Because it will be so key for you to listen to that episode to get the full story, to understand more of the background. So you can get the most out of this part two which we are going to hammer home this whole entire concept of numbness and more of the answers that you are wanting from this specific question.

Now, I am going to give a little overview of part one where we talked about the definitions, where numbness is a loss of sensation; we have sensory and motor nerves’ sensory gives us input and the sensations from our environment; motor gives us output or the movement and the function of our body; the anatomy of the lower extremity nerves. Understanding the network of nerves in the lower extremities is key. And that is something that looks basically like a tree with the trunk and the roots and roots from those. So that is a very good way to visualize this. And how the femoral nerve branches into the saphenous nerve and into the infrapatellar branch of the saphenous nerve; this is key here. That infrapatellar branch of the saphenous nerve is the key item here that we are focusing on mostly. 

And when you look at the saphenous nerve, in general, and the infrapatellar branch of it, that gives sensation from the inside of the front part of the knee and then down further the inside of the leg. See the first pick in the show notes and that’ll help you give a good idea, especially of that infrapatellar branch. You can think about where your bottom button or that screw is. And if you were to take just like your palm and put it right on top of it, that would give you a relatively good idea of the area that a lot of people feel with that numbness.

And this can also happen to other surrounding areas around the knee. But that infrapatellar branch of the saphenous nerve is the main player in this. And that’s been one of the most research and study that has impacted the numbness that people feel. It makes sense based on the anatomy of the nerves and the way ACL surgery goes. And when we dive into what happens in the surgical process and also our anatomy and the surgical incisions, the procedure itself, the graft type that is chosen, it’s not 100% preventable to avoid some of those, especially superficial nerves and those branches. So either some of them get cut or they get stretched; oftentimes, a little mix of both. And how common is this numbness that we feel, especially around the knee, ranges from 40% to 80% with many studies referencing somewhere around the 80s, and then some improve over time. It varies in the literature, but the one thing that we basically know is that it shows how normal it is.

Basically, most ACLers feel some type of numbness or change in sensation. This is the common question that I get—this is normal. Is this something that you can expect? And also what are the outcomes related to this? And so today we are going to dive into the graft types impacting that, what’s normal versus what’s not, some of the anatomical variations that play into this, nerve regeneration and healing, and your recovery of the numbness. 

The first thing I want to dive into in this part two episode is how the graft types themselves play a role and how common the numbness and feeling are. And so as we break down graph types, we have the big buckets of allograft which is a cadaver, and autograft which is taken from your own body. And the most common places are your patella tendon, your hamstring tendon, or the quadriceps tendon. Those are the main three that you’ll see in the majority of ACL reconstructions with autografts taken from your own body. Now in general, allografts tend to have less numbness just because we are not cutting another part of the body or impacting another part of where some nerves go. Because the allograft and the harvest of it have already been done because it’s taken from a cadaver.

Now, if we look at autografts that’s taken from your own body. We’re having to go into the specific area and cut in order to create your new ACL graft. And that’s either going to be on the inside part of the hamstring, the hamstring graft, the patella tendon which is going to be below your kneecap, and usually part of the bone below that, and above that, a part of the kneecap is taken. And then if you take your quadriceps tendon, then that’s going to be above your kneecap where your quadriceps is inserting. And a lot of the time there’s not bone taken from that, but sometimes there will be. 

There are currently no studies that really show the comparison of all three, as well as really targeting in on numbness or those types of sensations. But what we can tell is basically that people with a quadriceps tendon are probably going to benefit from less numbness just because of the harvest site and the way that the nerve innervations work. But then, if you were to put a hierarchy of, maybe it is going to be the quadriceps tendon, the patella tendon, and then the hamstring tendon. The hamstring tendon typically relays a little bit more of that numbness than the patella or the quadriceps. And these are based on the regions that they’re taken from. And if you combine that with the surgical techniques as well as with the anatomy. And that is my own personal thought on that, putting those pieces together.

In terms of what the research shows us, there is comparisons between the patella tendon and the hamstring tendon with a lot of the infrapatellar branch of the saphenous nerve comparisons with hamstring tendon autografts. And this will make a lot of sense because of where the hamstring tendons were taken. And it is more common to hear about more numbness because of where this hamstring graft is harvested from. And when we think about the inside of that knee and the medial side of that knee, that’s where we’re going to take it. Usually, it is the semitendinosus and sometimes it’s bundled with the gracilis. And so the gracilis is one of the groin muscles. And then the semitendinosus is one of the inner hamstring muscles in tendons. 

And when you look at the anatomy of the saphenous nerve and also the inferior branch of that saphenous nerve and you see that come across from those tendons into the front side and the inside of that knee, this makes a lot of sense of, okay, these are where these nerves travel. And if the incision is going to be basically where that front part of it is on the inside, then it makes a ton of sense because they have to cut through that nerve or parts of that nerve in order to get to the hamstring tendon. 

And just as a reminder, just remember that these nerves are sensory nerves, so it’s not going to typically impact any type of function. But it might impact that numbness feeling because when a nerve is cut, that is going to impact what you are feeling in the sensory of what that nerve is connected to. And so that’s where the numbness comes from. And that could be either from that incision, from the drilling, or maybe from the tools. But this makes a lot of sense, especially when we’re talking about harvesting a hamstring autograft.

And now to compare also my own personal ACL surgeries. I had hamstring autografts on both of my knees. On my right side, what’s very interesting, my right side was the first one in high school. And we chose a hamstring tendon because the surgeon was like, you need a hamstring tendon. We didn’t know there were options then, but that’s what we went with. And the interesting part about this is where my incision was to take my hamstring tendon. And it’s actually exactly where that saphenous nerve, the inferior branch of it, actually crosses across towards the front of the knee. And what’s really interesting is that my sensory for my right knee, when I touch in that area, it’s fairly numb. And probably a half of a palm size, it feels a little off. And then when I touch in that area, I actually feel a lot of weird sensory input into the other side, or the lateral outside part of the outside of my knee, kind of lower onto my shin muscle. It is very interesting anytime I touch it, and that has been the same for the past years and years and years. And it hasn’t changed at all. And that’s where it is, it doesn’t bother me really if I kind of put my finger on it. And you know, when I was working on my scar tissue, I noticed how weird it felt. But I do notice more numbness on my right side. 

And now let’s compare this to my left side, where I had a hamstring tendon, and this incision is different. Instead of the incision being on the front inside, it’s actually right where my hamstring crease is towards the backside of my knee. And if I could go back and ask these surgeons like, hey, why’d you do it this way? I wish I could. This is very interesting in terms of my left side because I actually have not really much numbness at all. And I don’t have as much of a weird sensory feel compared to my right side. My speculation is that when they did the right side and the incision point and where they cut, they had to go through more of my saphenous nerve of that inferior branch compared to my left side. It’s pretty cool. And this is pretty anecdotal, who knows? But it makes a lot of sense to me, especially with the anatomy and the surgical procedures themselves. I just wanted to share that anecdotal experience of my own ACL surgery and what I feel specifically from that. 

Now, let’s talk about what’s normal to feel and what’s not. And there’s a few things to consider here. One of the things I want you to think about if you’re listening and you’re close to surgery, is the timing of the surgery. If you are immediately post-op, the anesthesia and the type of anesthesia are going to play a role. You have general anesthesia that puts you to sleep. Then there’s the local anesthesia. The nerve blocks are a part of the local anesthesia. If you have a femoral or maybe an adductor nerve block, that might play a role in some of the extra numbness you feel. And you can reference the first picture to see how that plays into that. It shows the femoral nerve block and the areas that it should affect. It’ll be a little different with an adductor nerve block, but that can also play a role as well. But these are things that are going to play into that general numbness. The thing is, is that you’re also fresh out of surgery. Your body is like, what the heck just happened? It’s not sure really how to process that new sensory information from the incisions to the healing, to the bone tunneling, to the new graft. Especially if there’s an autograft, your body is like, what the hell just happened? And it is fair for it to feel that way because it’s basically like another trauma, right? That’s what we usually call it and say is basically we’re going to have to go back in there and redo a lot of work to make it right. 

Now, it’s in that healing process. And the one thing that you want to think through is once you’re out of this acute phase or this early post-op phase, then you’ll notice more of the numbness area kind of normalizing to what it’ll normally be. And then it’s a little bit of a waiting game to see, does it regain its normalcy and touch and feel? Does it only get part of it? Does it get all the way back or maybe not at all back? And now this is going to come back to the nerves that were either cut or maybe stretched. And now it’s playing that game of healing just like the rest of the knee. This is because that infrapatellar branch of the saphenous nerve and other potential superficial sensory nerves that branch off of that or around that, what we call superficial nerves or close to the surface, have been cut or impacted.

And as I mentioned earlier, most ACLers have some type of weird numb spot post-op. For some, it might be small, some it might be a little patch near the incision site, and for some, it might be more of something like a palm size, or sometimes it’ll run a little further down the leg or the shin. It’s different for each person. And again, after you listen to this series and see all these different possibilities which we haven’t even talked about some that are coming, it makes a lot of sense.

Now, this last point of some of what’s normal to feel and what’s not. One of the things with this is that if you think about the anatomy of this inferior branch, it crosses across the knee and there are different variations of different branches and people have with their anatomy. This can also lead to kneeling pain and anterior knee pain and sensitivity that a lot of people feel. And I think that this gets missed a lot and we shake this up to, maybe it is just the patellar tendon graft. But this still happens with people outside of patellar tendon grafts. But when you think about the harvesting of a patellar tendon graft, you’re still impacting the inferior branch of that saphenous nerve. So that is something to keep in mind. If you are someone who has been dealing with kneeling pain and anterior knee pain and some of that sensitivity, there isn’t as much research on this specifically testing. But we do see some, and it’s more common in patella grafts. But there’s a combination of things that may be related to the pressure of the incision, to the graft taken. But I do think that there is something related to the softness nerve that plays a role in this. 

And when we talk about expectations, what’s the recovery of the numbness at your knee? And will it get back to feeling normal? Will you get your normal sensation back? This is the ultimate question and really will depend on so many factors. And it’s honestly, no one can give you a solid answer to this, but let’s talk about what we do know and some of the expectations surrounding this.

Nerve regeneration is a very slow game. I want you to think about a turtle sprinting. They don’t sprint. It’s basically what’s going on here. This is the way that you have to visualize basically any type of nerve healing around the joint or in general in the body. Now, if you look at the third picture that’s posted in the show notes, the link. It’s an image of an actual cadaver of the inside of the knee, and you can actually see kind of how that inferior branch of the saphenous nerve comes on the inside of the knee and spreads towards that front side of the knee. And it’s pretty cool to see that. And it can actually give you a solid visual of, okay, if we make incisions there, maybe there’s drilling around there, the patellar tendon graft taken, the hamstring graft taken, if it’s on the front side incision. So many things that can factor into this. And look at how tiny that nerve is. 

I remember in PT school when we went through anatomy lab, I was so obsessed and it was so fun to basically look at the cadavers, dissect our own cadavers, and be able to really see the intricacies of the human body. It was one of my favorite things in PT school. And it was cool how someone honestly donated their body and we were able to learn from that. But, you can look at all the pictures you want. There’s something that is so unique about actually touching it, dissecting it, and seeing how there are anatomical differences from person to person. And this cadaver image gives you a little bit of insight of maybe what you see from pictures of, oh, here’s the show of what nerves and anatomy look like. And then there’s the actual cadavers in human individuals. And they look very different. It can look like just basically hairs or strings. And this cadaver picture basically shows that, and it’s pretty cool.

The thing that I want to bring to light here is what happens in each situation in terms of, okay, so there’s been a cut to the nerve. If the nerve has been completely cut either will slowly grow and try to find each other. If the two ends meet, the nerve will likely rejoin, and therefore sensation will return. I can’t say 100% that it will, or that’ll be the same. But there are a lot of times where these types of things can happen. The main thing here to point out is that physiology and research show us peripheral nerves or nerves that are in our extremities. They grow at a rate of one to four millimeters per day. If you’re looking at 30 days, it’s 30 millimeters or 120 millimeters, and that’s not really a ton. It’s probably more on the slower side of that one millimeter. It’s not a lot of distance, so you have to give it a lot of time. Sensory nerves tend to be a bit better with the growth capacity and can possibly recover over months or over years in some cases. This has been shown in the study by Höke in 2006, mechanisms of diseases, and what factors limit the success of peripheral nerve regeneration in humans. So that’s a little insight on a cut and basically the nerve regenerating if it can. 

And then another factor to consider here is if they’re stretched. Maybe with the tools in there or the way that the graft is put in, the nerve is stretched. Because of just moving around in the joint and trying to put it all together. So that is a very big possibility as well. If the nerve is stretched during the surgery, there is a much better chance of the sensation that it will improve. During the stretch, the outer part of the nerve will typically squeeze down and impact the blood supply inside the nerve. And that’s the example that I mentioned in the first part of this series where sleeping on your arm. But you’re probably thinking of a little bit more of a stretch and extreme example here via surgery.

And then sometimes during nerve healing, it could be normal to feel some of the tingling here or there, some of the electric feeling, maybe burning, pins and needles, all are normal and indicate that your nerve is somewhat trying to heal. Now, this can vary so much. And the thing that I want to make sure that you think about with that last point I made, is that you just want to make sure that this isn’t a longstanding feeling or impacting your function. To me, this might also help explain some of those weird, funky sensations throughout the ACL process. I’ll get questions about, hey, I feel this, or this sensation, or this pain. Now again, multifactorial and depends on what you’re doing and where you’re at in this process. But I do think that sometimes some of this can potentially be attributed to that nerve regenerating in this process.

Now, each person has their own individual case, so take that for what it’s worth. But some of those weird aches, and pains, sometimes can pop up, and then they just disappear. Who knows if that’s just that saphenous nerve, that inferior branch of it, trying to heal and recover? I know that I had tons of those throughout the process. Not only early on, but middle to late. You’re just like, what is this sensation? And then it just goes away. Or maybe it’ll come and go. Who knows if that is the nerve trying to regenerate or if it’s just the ACL process? 

Now, last few points here I want to make. Anatomical variations and this is going to be the last pick that you’ll see in the show notes. This is a pretty cool image but also highlights how people can respond differently. When you think about the different factors that play into everyone’s experience, you have a human body, you have genetics, and you have different types of pain and sensations based on your experiences. Because pain and sensory are all multifactorial. We talked about the graft types, we talked about the surgical incisions, the techniques, the way the tools are navigated, the holes are drilled, and anything that is being cleaned up, there are so many different pieces and moving pieces to this. 

The other thing that I want to add here that is part of our anatomy is anatomical variation. When we talk about the anatomy of nerves or the anatomy of really anything in our body. For example, when you think about the sciatic nerve on the backside of the body. Usually, that will be where people will point in their glutes. If they have some type of pain there and are especially nervy, then your sciatic nerve is going underneath that piriformis muscle. Now, there is a certain percentage of people who actually have that sciatic nerve pierced through the middle of that muscle as opposed to behind it. And then there are some people who have bifurcations or pieces that branch off of it. This is anatomical variation. 

The same thing can be said when you look at this image of the infrapatellar branch of the saphenous nerve. When you look at the different types of variations of that nerve and its branches, then you have to think about the little mini branches that come off of that. It’s just going to be innervating different parts of the knee, of the skin, all these different pieces and that is going to impact your sensation and your sensory and that numbness. This is a big one that I want you to take with you to know it’s going to be different from person to person. And then talking about the different factors of, okay, did they cut through that? Was that just stretched? Was part of it stretched? A lot of things to think about and some food for thought in terms of the anatomical variations. 

And one of the last things here that I want to talk about is basically just the expectations and the recovery. And basically, you walking this journey and figuring out, okay, is this going to recover and heal? Is this going to be something I’m stuck with? And the big thing that I want to really provide for you because it’s important to be practical and set expectations. And really just the transparency of this process. The further away from post-op you are, and you still have that numbness, the less likely it is for that to really and truly come back. And that’s just something that I’ve noticed after working with hundreds of ACLers. Our team has noticed that when you look and talk to other people who work with ACLers, surgeons, PTs, and all my friends who are also a part of, and in this community, we all talk about it and it’s very common for that to happen.

And as we pointed out in the statistics earlier, a lot of people do feel that. And a good rule of thumb to follow with neural regrowth, the generation is basically a year. Just know that there is also a good chance it won’t restore to 100%. Most ACLers would agree with me here, and that research supports it. I think it’s important to know that. So then that way you can understand, okay, I’ve just had my ACL surgery. All right, the nerve block has worn off, if you got that. I’m feeling a little bit of numbness. And maybe it’s on the inside of my knee, maybe it’s towards the outside, maybe it’s down the leg a little bit. Now, we want to make sure that doesn’t impact function, and we want to make sure that that does hopefully improve. But there is also a chance that some of that won’t improve, or maybe it’s something where it reduces in size more than anything. 

The one thing I’m here to tell you is that you really have nothing to worry about. It shouldn’t affect the healing of your joint, it shouldn’t affect your ACL graft healing, it should not affect your function should not affect your pain. For the most part that can get a little complicated. But for the most part, hopefully, it’s just some of that numbness and weird feeling, but not coming off as pain. And it should not affect your overall recovery and healing of this process. They did studies on this looking at people with and without numbness 24 months after ACL surgery and showed no differences in range, pain, or function. And that was for people who had an injury to the infrapatellar branch of the saphenous nerve in the anterior cruciate ligament using vertical skin incision for hamstring harvesting: risk factors and the influence of treatment outcome. This was a study by Ochiai in 2017. I apologize for that long title, but I want to make sure that you guys have the data supporting all of these things that we’re basically talking about and claiming. And there are similar findings in people with total knee replacements. So you can find that research as well.

Most times it’s just numbness and a lot of the time people get used to it. The majority of the ACLers I work with all get used to it. Now, the kneeling pain is going to be a future topic that we talk about. But in terms of that general numbness feeling, as long as it’s not impacting the function or your overall process, then most likely we’re good to rock and roll. Now, if you are worried about this, when in doubt, talk to your medical professional you’re working with. Make sure that it’s not affecting your function, and make sure that you have nothing to worry about. But for the most part, you’re pretty good to go. But just check with your medical professional if that is bothering you and you just want to be on the safe side.

So that is the two-part series on: Is numbness normal after ACL surgery, part one and part two? Thank you guys so much for listening to this two-part series. I hope that it was helpful. And don’t forget to check out the show notes where we have some of the images. If you want to geek out, it’ll also make so much sense. I know for me, I’m a big visual learner, so seeing the nerve and the anatomy, the variations, and even like that cadaver picture of the knee joint and that nerve, it helps to really hit home of understanding all of this and the process. 

If you have any questions at all, please send me an email. Hit me a message on aclathlete.com or a message on Instagram at ravipatel.dpt. And I would love to answer any questions that you have or any thoughts you have about this podcast series. But other than that, I just want to say I appreciate all of you. Thanks for hanging out with me, and for giving your time and your attention. It is always so valuable. If you feel like you got value out of this, or the podcast is giving you some value out of your own process or your own experiences, please do me a favor. And rate the podcast, and give us a five-star review. 

My goal is to be able to share as much education so we can equip all of you to make informed decisions. And so then that way this could be something where, hey, like if you’re experiencing numbness and you came to this episode and you’re like, man, I feel at peace because of this episode, and I understand what’s going on. Not just being told, oh, it’s normal and a part of the process. No, we’re going to give you the why behind it and the practical pieces. That’s the main thing with this podcast. We want you to be able to be in the driver’s seat in control. If you can give us some love, that would be so appreciated, whether you’re on Spotify podcast, Apple, or any other platform. You guys are the real MVP. Now, I’m going to go and drink some water. Stop talking because my voice is going hoarse from recovering from sickness. But hey, we’re here, we’re good. 

I hope you guys have a good rest of whatever day, time, whenever you’re listening to this. And until next time, this is your host, Ravi Patel, signing off.