Episode 123 | 0 Degrees Extension – Good Enough for ACL Rehab?

What is up team, and welcome back to another episode on the ACL Athlete Podcast. We are talking today: Zero Degrees Extension – Good Enough For ACL Rehab? Basically, we’re trying to figure out how much extension is good enough. This is something that we get really often as a question from our own ACLs. People reaching out, clinicians, coaches, even surgeons who are like, hey, like what do you guys look at as far as the normal extension that you want to see? And if you’re listening to this, you might also be wondering, is my extension normal? And you’re just like, I want to be at peace with the world with my knee, can you please answer the question? 

We’re going to get down to the details of this, especially if you’re sitting here saying, oh, well, I’m at zero degrees extension. Well, let’s decide and see if that’s enough. And to make this super simple, extension is where you straighten your knee and it’s fully straight. And then flexion is where you’re bending your knee or bringing your heel towards your butt. And now these are two range of motion type goals we have in ACL rehab, whether you are post-injury or post-surgery. And people’s extension, range of motion, and even flexion for the most part will be pretty similar, although there are going to be anatomical differences from person to person based on our genetics and the way we are as humans.

And typically, we see a lot of this trend from our own family where if you have bow legs, typically what we’ll see is a parent or someone who has that. If someone has flatter feet, which of course is not a problem. But you typically see that somewhere in the family, usually mom or dad has that. Same thing with extension and especially with someone, let’s say, where they have hypermobility where there is an increased range of motion. We tend to see this more with female athletes who have an excessive range of motion or are super flexible, kind of like Gumby. And so they might have a little bit more of an excessive extension where they’re hypermobile. These can all into, all right, what is a normal extension? And while there are different variations, human to human, we do have normative data and we do know the normal ranges that people typically sit in. And we’re going to dive into this. 

And the reason that this podcast episode comes up is sure, it’s a question that we receive often. But I think it’s also a major issue in our ACL rehab process, and it’s something that, you know, not even us are immune to. Because at the end of the day, we are at the mercy of our bodies to some degree, but we gotta make sure we facilitate that extension, working on it, making sure that that’s one of the big rocks you’re focusing on if it’s not fully restored, early post-op, early post-injury. And so this is the thing that we will often see because a lot of times ACLers will reach out for our help, not necessarily pre-op or post-op which does happen. But a lot of times what happens is they’ve run the normal course of their insurance or whatever that might be, that is their local care, and they start to realize, oh wait, I’m not either making progress or I’ve run out of visits. And then they’re looking for the next option, or they’re just honestly just feeling lost. That’s how most people end up coming to connect with us. And when we see and talk to these athletes, a lot of the time these are complex cases because maybe there are multiple tears, they haven’t gotten their extension back, lacking strength, they’re dealing with pain, swelling, not running yet. You name all the things that many of you have probably thought through your head or you’ve heard about in this process. And this is not uncommon to see that. We will have an ACLer talk to us, three months out, six months out, a year, two plus out, and they’re like, I never got my extension back.

And so that’s something where we’re like, okay, well, this is going to take a little bit of testing to see how this looks and feels, and also how does that play into your bigger story. But I would probably say with the people that we work with, if they come post-op, especially post-op, because if you’re post-injury, you might not have been exposed to all of the things you need to be doing, and your knee is swollen and angry from the injury. Typically, most people go and see a surgeon or an orthopedist, then they go into physical therapy if they’re lucky, and then potentially surgery. But hopefully, whenever they walk into this post-op process, they have had the joint normalized. And they’re set up with a good solid start with brand new ACL or whatever repair that might be within the joint to be able to kickstart the official journey if they want that route.

So with that, hopefully, extension has been a big factor that has been emphasized to achieve the earlier, the better. And I would say that probably three out of four ACLers who reach out to us come in with some sort of extension deficit. It’s just the thing that we see, and I think it goes hand in hand with people with complex problems, or maybe it just wasn’t emphasized enough in ACL rehab. And this leads me to the title of this episode anyway, because what ends up happening with this is that people will often hear that after post-op their surgeon or their PT will tell them, oh, you don’t really need hyperextension, zero is good, or neutral is good, or maybe you were immobilized for a long time. And then it made it really hard to get even close to zero or neutral. But that’s the thing that we will see often. And at this point, after seeing thousands of knees, the majority of knees go into hyperextension. And we’re talking somewhere around 5 to 10 degrees past zero, so what we call minus or negative extension. Hyperextension is 5 to 10 degrees past that zero.

For example, if you were to lay on your back on a treatment table, and if I were to take one of my hands and stabilize the end of your thigh bone, so right above your kneecap before your knee joint starts, if I just push that down or stabilize it, and then I just easily lift up on your heel without you contracting your quad or trying to extend. I’m just going to lift up on your heel. You should do what we call passively because there’s no muscle contraction, and be able to come up off the table in most cases. So that means somewhere around 5 to 10 degrees with the majority of people.

And these are tons of knees that I have checked. I’ve seen my own knees. I see tons of other people. And even as a team, we talk about this, and this is something that is pretty consistent across the board. And the thing that helps with this is that the textbooks back us up, of course, which is where we will base our foundation which is based on research of normative data. And usually what those will typically track, depending on the source, is anywhere from five to seven degrees of hyperextension, give or take a little bit with the exception of people who might not go all the way there. And I have some athletes right now who I’ve tested and they are sitting at zero degrees and they might be at minus two degrees. And then there’s very rarely people who sit in the positives just to the nature of our anatomy and the way that we are built. Long story short, we go into hyperextension. It’s normal. And if someone says, “Hey, you only need zero, and you don’t need any hyperextension,” I strongly disagree. Based on a number of things from the way that our mechanics and biomechanics work in our joints, to the way that our muscles activate, to the different movements that we do in life. This is something that should be natural. And the way we anchor this is to the other side. That’s our gold standard. 

But before we get there, I want to talk about why some professionals might say zero is good enough. I’m honestly not sure. And I think it might be just a lack of information or assuming like, oh, hyperextension could be bad without diving into too much of the details. But hopefully, they are digging into the foundational knowledge of the way our human body works. And in the majority of cases, we go there. It could just be not knowing why. And then the other thing that I think does come to mind is that within this process, the further and further you get out from post-op, it could just be a nuisance a little bit. You guys all know this process of just working on your extension constantly. If you got it really early, that is awesome. I’ll be honest, for myself, I didn’t really deal with much extension, but I also cranked on my knees really hard because I knew it was an important thing. And my PT that I was working with really emphasized getting your extension. And so that was awesome.

The thing is, is that I think because of the people who potentially struggle with this, you name the number of things post-op from the pain to the fear to the quad, mind connection of feeling that quad and contracting it, nerve blocks, all these things that play into, oh, why it could be hard to work on that extension. Some of it could also be because, well, the protocol says so, or we’ve had some athletes who come to us and they’re like, yeah, the surgeon said not to do anything for two weeks, or scheduled your PT two weeks after. I haven’t been doing anything that in 99.9% of ACL cases, no matter the complexity of the injury, you should be at least starting to work on extension day one. And you can do something to some degree and it’ll make a massive difference in those first four to six weeks, especially the first days and two weeks after surgery.

This is something that I just find very interesting because I think what happens is that these clinicians or surgeons or professionals who say like, zero is good enough. Well, they probably just want to progress them and the patient along that timeline. Or the patient might be asking, oh, if it’s normal, and they might have this answer where it’s like, yeah, it’ll just get better with time and then they don’t revisit it. It’s a good enough gray area where you’re not bending with a 20-degree extension. You’re maybe around 5 to 10 degrees, maybe zero. And like, ah, it’s good enough. You’re able to do most things and things don’t look weird, for the most part. So yeah, that’s fine or it’ll come. And I think it’s also one of those things too, where you’re kind of in a rock in a hard place where if it’s not progressing, then maybe it’s just zero is normal, it’s fine. But I think that it’s something we have to be careful about given each specific person and trying to achieve as much hyperextension as possible. But most importantly, using your other leg as the gold standard. And I know that can be frustrating, but your other knee is going to be the thing that you want to reference more than any other person’s knee or what these normal values are. 

For example, the athlete I have who has pretty much zero hyperextension on her uninjured side, that’s kind of our target. We’re not trying to push her into 5 to 10 degrees of hyperextension because she’s an awesome athlete. She tore her ACL in a contact injury and she is good at zero degrees. We’re going to get her there and not any further. But, for most people who are sitting in that 5 to 10 degrees, we’re going to try and get there. If you are someone who is hypermobile or if you see some people stand and they really have that curve backward, that could be something where they might be in the 15 degrees or 20 degrees of hyperextension. That might be a little too much, and we don’t necessarily need to go all the way there. There’s a sweet spot where you probably want to be in the minus 7, minus 10. But again, this is going to depend on person to person based on what it is that they need, the quad contraction, how they feel, and then also how that translates into more functional and dynamic tasks. 

And the last example I’ll give here that might be a little too far is that one of my athletes achieved extension pretty quickly. He ground it out and made sure that he was focusing on it. He got his heel pop. It looks beautiful. And the thing is, is that he almost went in the opposite direction and started cranking on it a little too much. And with that, what ended up happening was he started to notice that the knees started to get achier when he started to hyperextend it too much. Then what I had told him is like, hey, let’s just get it to match up to the other side. You have good hyperextension. It’s a heel pop. The height of the toes is even, and that’s all we want. And so that’s what his goal and the knee pain went away. What I suspected was maybe just different contact pressures or the way that the patella was interacting with the femur and the contraction points and all this was playing into aggravating that kneecap. Once we cleared that up, he was totally fine. 

And it’s very rare that people have normal resting zero degrees as their normal. And I know that the focus of this episode is zero degrees good enough because that’s what often surgeons or physical therapists will tell athletes in this case. And the thing is, is that most people don’t. The only time that people do is if it matches that unoperated side, just like one of the athletes I have. And they feel 100% solid in the knee with no issues, and that translates over to their strength and the dynamic tasks that they do. 

And so why do we care so much about extension? You’re like, extension, extension, extension, I get it, Ravi. But we have to care about this because it is truly when I think about a foundational piece when I think about laying that brick-by-brick foundation, extension is a massive part of this. The reason we carry is that research shows a number of things related to extension from the risk of osteoarthritis, with it being in a resting state of 3 to 5 degrees of extension. There’s just a slight bend when people stand. The joint arthrokinematics, so the way that they interact with each other. You want to make sure that that femur and that tibia glide on each other like normal. And when they don’t and when there’s an impact based on that extension, there’s going to be stress in certain areas that… 

Let’s say, for example, when they’re standing or sprinting where the knee does get straight, that’s going to be impacted because the stresses are going in different places. And then the same thing with your patella and the way it interacts with your femur bone. And how those arthrokinematics, basically, the movement of the bones and how they interact is going to look a little different because you’re not getting that full range of motion. The caution of progression of exercises with this is because of those high compressive forces or what we call shear forces when they slide back and forth because it just creates contact pressure in certain areas. Now, it’s not necessarily the worst thing ever, but we have a normal state of our knee we want to have, so that’s supposed to be our goal.

The other thing that I want to add to this is when a knee stays in a state of zero or even a slight bend, there can be a shift in those ground reaction forces anytime we step to the ground. Anytime we take a step, the ground is pushing force against us, and that can push that line of force a little differently when the knee is straight versus when it’s bent. When we stand in normally, it usually goes in front of us. Whenever we have a little bit of a bend, it goes behind. Therefore, that impacts the muscle interaction or the moments on our knee where basically our quads are kicking on. And you would think that this is a good thing, but it’s not. You don’t want a constant state of contraction whenever you’re in extension.

Hopefully that all makes sense, okay, why do we care so much about an extension? And to hit this home, it increases areas of patellofemoral stress as we had just talked about, wear and tear to certain articular cartilage, what we call screw home mechanism, where the joint turns a little bit whenever it goes into extension and rotates. From the more practical pieces, it can impact quadriceps activation and strength into normal gait mechanics, to running mechanics, to things that go beyond that, like running, jumping, and cutting to strength pieces to just stress on your patellar tendon and joint stress. While you might be sitting here and you’re like, oh no, I’m freaking out. I don’t have my full extension. 

One is to continue to work on your extension. We’ve had athletes months and months and even years out, be able to make some gains on their extension. But of course, I do want to talk to you about what if you fall into this bucket of, I’ve worked my butt off on extension and I’ve done everything imaginable and still can’t get into hyperextension. Is zero good enough? I’m going to try and tackle this question because I want to make sure that those of you listening don’t feel like you’re doomed if you don’t have your hyperextension. Because I’ve worked with plenty of athletes who don’t necessarily get all the way there and they’re completely fine. But there’s some caveats to this. And so I want to talk through those different pieces because I think it’s important to walk through that and understand where you stand within it. 

The first point I want to make here is that when zero is good, as I’ve already mentioned earlier, it’s when you’re uninjured side. The side that has not been operated on or uninjured, is the side and it sits at somewhere around zero. And that’s your normal benchmark and you’re going to be good to be able to be at zero. Because that’s where I think that it should be if that’s you’re human being, normal state. Usually, everything within that, if that’s your normal place, looks good, feels good, feels normal. You’re not having a ton of pain or issues with those contractions, and you get a really strong quad contraction. That’s the other thing that pairs hand in hand with this. Is that if you have a missing part of the extension, especially into that zero, into hyperextension, then it is harder for you to get a really strong quad contraction where you really engage. It’s like trying to lock out your tricep, and your elbow, and trying to squeeze your tricep as hard as you can. 

But you can’t lock out your elbow all the way. Well, you can feel your tricep, but it’s not going to be nearly as strong contracted as when you go into that hyperextension of your elbow. Weird how your elbow works as a similar joint as your knee, a little different, but similar. And so this is one of those things where you’re like, okay, I’m at zero. My other side is at zero, so I’m good. 

Now, let’s talk about another option. Maybe you are someone who had a pretty complex injury where there might have been some fractures or the knee really took a hit, especially if it’s a contact injury or the joint isn’t necessarily responding to any type of extension work. And so that’s the thing where we just have to work into this and see how is the knee status, what was done, and then also what was the work that was put in to help get it into that hyperextension. This could be due to a number of issues that can arise. And I want to talk first about the structural pieces that can be something that’s in the way or restricting it, such as scar tissue, cyclops lesions, maybe a meniscus tear, bone bruising can kind of play into this, of course, a fracture, graft site pain will actually play into this. I’ve seen plenty of athletes who have discomfort, they get a quad tendon, and that last little terminal extension bit is hard to contract because they’re getting a lot of pain at that graft site where they got the quad tendon.

Guess what? When you try to lock out your quads, you feel that pain where it’s pulling on that quad tendon. So that can be a limiter to get there, usually, people can get there. The thing is, it can almost make people apprehensive to get there or feel that pain. There’s of course, the lack of strength or the input and activation to the quads, so we might be talking about arthrogenic muscle inhibition, or maybe is just a really weak quad that doesn’t want to wake up from the nerve block or post-surgery or post-injury. And then potentially other repairs during the surgery or any type of surgery that has happened. So that’s the thing where sometimes people have a meniscus repair or LCL or MCL repair, or maybe they had to get a plate screwed on to mend their bone back. There are a lot of things that can happen.

The other thing may be a LET (lateral extra-articular tenodesis). Those are all things that can play into this. And can impact your ability to get an extension from actual, physical, structural blocks to actual pain, swelling to structural limitations that were done within the surgery or that might be impacted because of that pain and swelling. Just things that can be factors. Of course, every single person is different and I didn’t even name all of the potential options that could happen here. For example, scar tissue, and cyclops lesions, those things are very real. We have had people more often than you would think, who can develop a cyclops lesion. I think that cyclops lesions, personally, and this might be because we also get a lot of complicated cases, that cyclops lesions do happen a little bit more than the percentage that’s given in research. Take that for what it’s worth with anecdote, but usually, people get ‘them cleaned out and they do a lot better.

And that leads me to the next point, which is whether or not you have really worked on your extension, whether it is post-injury or post-surgery, especially the post-surgery. Because at that point there has been an assumption that the knee has hopefully been restored to where it needs to start healing. And the joint itself has been checked, hopefully by the surgeon to make sure it can get there. Now, the goal is hopefully that you’re not told to not do anything for two to four weeks. And this is something where you’ve been hammering extension and it still is not improving. And that’s the thing that we want to make sure we know is you’re doing the right exercises, tracking it, and it’s still not improving.

Typically, people can get close to that zero. They might be a little shy about it. They might get into a little bit of hyperextension when they warm up a little bit. It just kind of varies. But what I want to basically like end this episode with, is if you’ve literally exhausted every option. This includes working aggressively on extension. You might be at 8 weeks or 12 weeks or 16 weeks further in the process and it almost feels like it’s plateaued. You’ve still been aggressively working on extension and of course, there are some clinical signs and some testing signs that are showing maybe like we need to get an MRI. And you get the MRI, and let’s say you do have a cyclops lesion or scar tissue, then hopefully the goal is to get that cleaned out and continue back on the course to work on your extension and get that back to normal.

Let’s say that happens and there’s nothing there. There’s nothing there, and so then maybe there is a consideration of a manipulation under anesthesia, what is called MUA, or potentially a cleanout surgery because something is sitting there. We’ve had athletes get this for a number of reasons that I had mentioned, and they tend to get back to doing what they want to do and get that extension back. Sometimes it can regress a little bit and not as perfect, and this is just being completely transparent with the needs that we’ve seen, the way that people’s bodies adapt to this ACL rehab process, and the work that they’re putting in.

And then if you have exhausted all things. You’ve worked on it aggressively. You’ve done the MRI, maybe there was a clean-out to help do it. Maybe there was a manipulation on your anesthesia, or maybe the surgeon’s like, hey, you’re kind of good enough and you’ve been working on it as hard as you can. Zero can be fine, and I want you guys to know that. It’s just going to really depend on the person because there are plenty of people who their body just accustomed to that being their new normal, and that’s totally fine. The biggest thing here is that we need to make sure that the quads can activate and squeeze really well. That is not a contributor that is playing into the constant pain that you’re dealing with and making sure that you can build up your strength. Making sure that it is not impacting things functionally from pain to gait, to strength, to dynamic components like running, jumping, cutting, and those are the things that we want to make sure are in check. If you are this person who has exhausted that route and is still sitting with some extension deficits. It’s okay. Just want to make sure that we do as much as we can to minimize that risk given the things that I had mentioned that contribute to not getting your full extension back to normal. 

And I’ll leave you guys with this last story of an ACLer that I worked with when I first started really working with ACLs years ago. She was an older athlete. She loved playing pickup soccer. And she had torn one ACL years ago, and she still had some deficits in that knee. She had just dealt with it, still lacking some extension, some strength deficits. Someone cleared her and then what happened? A few years later, she went out and she tore her other ACL. Yep, that sucks. She had ACL reconstructive surgery. She went somewhere else for her rehab. And then of course, here she comes and I get to work with her after two ACLs and then her knee was just in this like mess in all honesty. She had not been able to bend her knee very much. She was super stiff.

The thing that was interesting about her is that she actually had had already two to three scar tissue cleanouts. And what we learned about her is that she was just someone who was very prone to laying down scar tissue, just tons of scar tissue. When you looked at her MRIs, you could see the layers of scar tissue within there. You could notice the puffiness of the knees. And then also just like the kneecaps not wanting to move the joint restrictions. I think that this is one of those things where it’s like, all right, so she had an injury. And then her genetics did not play to her advantage of her having the ACL reconstruction. And while some of you might be thinking, hey, that’s me, it’s hopefully not. And this was a very rare and unique situation. 

And since then, I have not really come into contact with anyone who has had that much of a similar issue as that person did. Now, you just work within those constraints of it and you get them back up to speed of what they can do, build up the things that we can work on and the controllables. And then from there, we also have conversations about the goals and what it is that still brings them happiness. And if it’s continuing to pursue that thing, we work within those constraints. If it’s pivoting to potentially, sorry for the pun, not good for the ACL podcast. But this is something where we have the conversation of maybe it’s shifting the goals potentially based on their history. Of course, for us, we’re always going to try and get you back to the thing you want to do. But if you’re sitting here with three, or four ACL tears and you want to go play soccer and you’re a dad of three kids, it might be a different conversation. And that’s a podcast episode in and of itself. 

But today, I just wanted to touch on this because I think it’s something that happens way more than we think of people thinking they only need zero degrees of extension. If you’re someone who’s early in this, work on it as much as you can and use your other side as the gold standard. And if you are someone who has been working at it and you’re just like, “Man, I’ve exhausted all my things.” And then it’s a matter of all right, the expectations of this process and making sure is this impacting the rest of my journey and the things that I want to do. That’s the conversation you have with your provider, and you create a game plan to make sure that is not a disruption and it’s not a barrier for you to get back to the things you want to do. 

All right, guys. That was way longer than I expected, so I apologize. Thanks for hanging with me here. Appreciate all of you, each and every single week who do spend the time to just listen. We appreciate your support and we’re going to keep doing the thing. Until next time, team. This is your host, Ravi Patel, signing off.