Episode 179 | What Shin Angles Tell Us About Your ACL Rehab

What is up guys and welcome back to another episode on the ACL Athlete Podcast. Today’s episode is what shin angles tell us about your ACL rehab. First, let’s lay some groundwork for this episode. I want you to picture this. You’re doing a lunge. You step out with your leg, whichever one you want to do the lunge. And if you’re an ACLer you’re going to step out with your ACL side, the one that has been injured, or you’ve had the surgery on and you’re stepping out with that leg to do the lunge. 

Now, your shin is your lower leg bone. This is going to dictate the shin angle. If the angle at your knee joint is 90 degrees, your shin will be neutral or perpendicular to the ground. Basically, you get your vertical shin and then you have your femur or your thighbone meeting it. You have a 90-degree angle and that is a vertical shin or a neutral shin, that is 90 degrees at your knee joint. It’s that perfect right angle when we were in this lunge, in this situation. Now, if the knee moves forward towards the toes or pass them, this is called a positive shin angle, where that shin goes from that neutral position and your knee starts to drive forward over your toes. Your knee starts to make your toes disappear or your foot disappear. So that is going to be a positive shin angle, also is moving in that forward direction. And then for negative, you can think the reverse of this. If we go back to that neutral position or the knee is in the 90-degree position, this shin is vertical. If the knee moves backwards or you’re able to see more of the top of your shin bone, if you will, then that is going to be a negative shin angle. 

Honestly, a negative shin angle in a lunge is generally hard to do. It’s mostly used dynamically, like when we’re doing decelerating type of work, when you’re running and you need to decelerate and stop. Your knee goes from this negative shin angle into this neutral to positive shin angle, is depending on the task, but that’s where a lot of this is associated. It’s usually not with a lunge, unless you’re putting a lot of back pressure or emphasis on the back leg of a lunge. And you are really trying to let off that front leg, or maybe it’s being awkward. You’re doing a little bit of a stanky leg or something. But usually in a lunch situation, that knee is probably going to be in somewhat of a neutral, that vertical position, or maybe driving forward. This is what I want to make sure to set up this visual to help understand as we talk through this episode, with the positive shin angle being such a key part of this. You’ve got the neutral and then you have the positive shin angle or the knee is moving past the toes. If you go back to neutral and is moving behind the heel or backwards, then that is a negative shin angle. Now, why do we care about this? This is something that we categorize under our movement quality bucket or our positions and motor skill. This is something that we want to attain. When you go through our mentorship, or when we talk as a team, when we were assessing athletes, one of the things we’re looking at is: Can this athlete access their positive shin angle? Can they get that knee forward over their toes? Now, before we get caught up in knees-over-toes-type situation and that whole line of thinking, we’re not trying to go so crazy extreme over knees over our toes. There’s always a middle ground, but we want to be able to access, being able to drive our knee forward. Our foot typically staying flat on the ground and being able to drive our knee past our toes, comfortably. 

This is something that we’re looking to do and is something that is huge for us from a qualitative standpoint and movement quality standpoint. We are assessing this with every single one of our athletes, especially once the time is right. Are we expecting this to pop up one week post-op or post-injury? No, you’re literally in pain, your knee hurts. You can’t turn your quads on. It’s hard to do all the things. You don’t have that flexion yet. This is not expected immediately post-op. But as some point in the process, this is something that we’re hoping that the athlete can access. This could be something that potentially can be accessible anywhere from four to six weeks, very slowly post-op, especially once athletes are getting into two to three months, especially four months. Post-op. We’re hoping our athletes are able to access this because this is going to open the door for so much more. And if they are not able to check the box on this prerequisite, that’s a concern for us. 

Before you go listening to this whole episode and you get to the end of this and you fall into this bucket of, you’re not in this “timeframe” and you don’t have access to it yet. Don’t worry, this is something that we want to make sure is addressed. But there are plenty of athletes we see who don’t have this until later, usually they are somewhere else. But with that said, this is something that you can achieve later and something to work on. But just know everyone is not perfect on this timescale. There have been people who have just had it come later due to a number of issues, whether it is flexion delay, whether it is the quads or just not wanting to progress. AMI is a big issue. Maybe they’re dealing with some significant swelling and pain. Those are things that can play into this process that doesn’t necessarily tee you up for having this positive shin angle super early. So that’s okay.

With that said, I want to talk about some of the things that we would do to assess this, in general, some of our screens and some of our evaluation pieces. We’re going to look at this as side to side with certain aspects, even with a bilateral or a double-leg stance, even with squatting and things of that nature. But it’s very apparent, especially with something that might be a single leg or like a split-stance-type position. Some of the things we’ll go through is a Y-balance just to see how they can do with multi-directional reaches, being able to use the eccentric strength of their quads, we’ll look at split squats, 4-way lunges, walking lunges, a single-leg squats box, etc. Basically, a lot of single-leg knee-dominant-type task where their quad and their knee is going to have to work in order to bend and extend in order to tell us, can they do it or not? And then this also plays in dynamic tasks. When we talk about bounding, single-leg hops, vertical jumping, decelerating firmer sprint, cutting at different angles, etc. We have these static tasks, if you will, or maybe gym-based. There’s functional ones, there are strength-based ones and then there are ones where they’re going to be more dynamic in nature or more of our on-field rehab, on-court rehab type stuff, where we’re doing jumping, running, cutting, all the things. 

We’re looking at all this stuff to see what can we see that is going well? What is this stuff that maybe we need to work on, that are the gaps in what we are seeing and what we need to address.That’s what testing should expose. If you’re testing and you’re in this process, it should highlight some things that aren’t going well. You want that to be honest because then that stuff you can work on. That’s awesome. Unless you are at the return to sport process and you’re like ready to get back to the thing. That’s when you’re hoping that both legs will perform at the same way. Other than that, you’re probably going to have some deficits and that’s something that should be normalized. Don’t be down on yourself when you do have an assessment because these are things for us to work on, and those are good things. We just need to make sure we capture those things appropriately. 

One glaring problem that I consistently see with ACLers is this positive shin angle. I see it all the time. I kid you not. It’s just the lack of achieving this position. And the reason why it is so important is because it really does translate so much into a lot of the strength training exercises that we do into the dynamic task. I see people compensate all the time to just do the thing and they end up not being able to achieve this positive shin angle and it does become a problem. I’m going to share a little bit more here in a second about how that is playing into athlete’s case I’m working with right now. And the thing that I want to really point out is with this positive shin angle—why do we see this problem? Well, when we think about what’s required to achieve it, if we reverse engineer, and we talk about, if I want to access this position, what do we need? Sure, there are a lot of things that could be named, that could be a part of this that is required, but I’m going to give you the straightforward pieces that we would look at and most rehab professionals would look at in order to make sure we can achieve these positions. 

Number one is going to be ankle dorsiflexion. Can you bring your toe up? And especially whenever it’s on the ground, can you be able to drive your knee over your toe, where basically you have enough bend in your ankle? If you pointed down this plantar flexion, if you pointed out this dorsiflexion. But it is a little different whenever you have the floor versus you are just freely moving your ankle. There are athletes who just kind of run into a wall here, whether it is a history of, maybe it’s ankle sprains, maybe they’re a basketball athlete and they have dealt with some ankle dorsiflexion mobility limitations that limits their knee from driving forward. It might not even be a knee thing; it might be an ankle thing. This is something that we have seen with the athletes and it’s something that we would want to make sure we assess if this is a problem.

Then the other things, especially coming back to the knee is going to be, how’s the pain and how has the swelling? Because we want to make sure there’s no pain or little pain and little to no swelling because those two things are going to impact. Whether you want to drive that knee forward because a puffy knee is not going to feel good. To be able to do that, it’s going to feel full when it bends. And whenever you have pain, especially in the front of the knee or in the joint, it’s not going to want to keep moving forward because the more it moves forward, the more pressure and stress it’s going to create on the knee joint. So that’s why a lot of people keep that shin very vertical because it helps to de-load that knee joint a little bit and shift more towards the hips. We want to make sure that there’s little to no pain and swelling. Flexion probably needs to be somewhere around 120-ish comfortably. If you’re at 90 degrees, think about it, if you have 90 degrees of flexion and you’re in that lunge position and you don’t have any more flection or you feel like you hit a wall, that’s going to feel pretty terrible. And so then therefore it’s going to be hard for you to get a positive shin angle because you don’t have any more access to knee flexion. We need to have enough to be able to drive our knee past our toes, which is probably going to be around 120-ish degrees; probably a little bit more than that to get there comfortably. But that’s a good target for you to be able to get there. 

And then the other piece that I’m going to mention here is going to be quad strength, specifically eccentric quad strength. So that’s your quad is tensing up as it’s underload whenever is lengthening. When your knee is bending, but it is being tension with your quad, concentrically, whenever you are bringing up. Being able to do a knee extension, essentially, where you are straightening out your leg, that’s shortening that quad muscle or concentrically. And then when we think about a lunge, for example, your quad actually has eccentrically control that. Think about stepping off of a stair versus stepping up onto a stair, stepping up onto a stair would be concentric. And then you are looking at eccentric, which is, think about stepping off the stair down the stair or going downhill, for example. Your quads are working in an lengthened state in order to do this. 

I know there’s a lot of nuances with this conversation. But I hope that this makes sense for you guys because It is really an important thing that I do want to elaborate on because I think it will be helpful for many of you. Because this is missed so much, even with PTs who are saying, they’re paying attention. To be honest, this is one of the biggest things that I see, and it’s a glaring issue. It’s one of those things where it’s so important to address, but it gets missed all the time. I’m hoping that this can help to highlight a few things that you can even look at yourself, or if you’re a physical therapist or coach looking at this, making sure to use your coach’s eye to dial in the qualitative movements that plays into all the objective testing we’re doing as well. All this makes sense, right? Ankle dorsiflexion, little to no swelling and pain, flexion needs to be at a comfortable 120-ish and then quad strength needs to be there to a certain threshold, specifically the eccentric strength of it, or when it’s being lengthened. This all makes sense, especially the quad strength and honestly, the quad strength and majority of cases is the problem. 

What happens with this ACL process? Your quads just die. They just go somewhere and they die. That’s a little dramatic, but seriously, most of you are probably shaking your head. I feel like my quads dead. Where is it? And so this is something that is just the nature of this injury. It takes a hit to the quads more than anything at all. If you have a quad tendon—I’m sorry—but you’re getting even more of a hit. This is something that is very common. That’s why the quad strength is something that is usually the big limiter or what we call a rate limiter. Think about it as a bottleneck, something that is basically stopping the process from being able to move forward or limiting that process. People start doing these movements where it needs more quads, such as lunges, maybe your protocol or your PTs like, “All right, let’s start doing lunges.” You’re at week six or week eight. By the way, lunges are pretty advanced. I think protocols typically have it wrong. I would delay lunges for quite a minute for my athletes. We work on a lot of other stuff to make sure we can get the knee and the quads more dialed in before we start dialing in too many lunges. 

Because of the demands of it, we just want to be very mindful about the progressions. And the thing is, is that athletes will start doing them because their protocol RPT says to and they do it. But it looks different side to side and typically they just don’t have the capacity or the strength that. So what happens? Well, if I ask an athlete to still do the movement, guess what, their body is still going to find a way to accomplish the task. Typically, the shin will stay more vertical with this. If it’s the ACL side that is stepping forward, it is going to essentially be the shin is going to be perpendicular to the ground, or it’s going to have that 90-degree angle that we talked about earlier. 

Some other things that we might notice is that there’ll be more bending at the hips and leaning the trunk forward. And what this is going to do is bring the glutes and hamstrings to the party to get the job done. What we were trying to do is avoid using the knee and the quads and we’re doing the movement. You’re getting some assistance from other areas. This brings up this new athlete that I just recently evaluated. We went through our assessment and she could technically do all the movements. She was months out. They were having issues, the quad strength, not feeling a lot of guidance with their current PT and structure. We dial things in and we did an evaluation. She could technically do these movements. I asked if they felt the same side to side, and if she noticed anything while we were doing them. She said, “No, they felt the exact same.” Then we looked at the video feedback and I pointed out some of the differences that we noticed with just different compensation patterns and different things we were seeing. 

One thing that we saw was, when we assessed, looking at a walking lunge and some of the other variations to see what the knee was doing with movements like this, we were able to see one shin was totally vertical and the other one was way past our toes—drastic differences. She and her mom thought it was normal. When we looked at the videos, when we were looking at it in real life, when she was reporting how she was feeling, it just felt normal. She was able to do a lunge. It just looked different the way she executed it from side to side, but they didn’t see that. And this isn’t something that I’m expecting for them to see. But I was just curious, can the athlete notice it or feel it? I always want to make sure if that’s something that they notice, then great, they know is something we need to address. But if they don’t notice it, then we don’t know it’s a problem to address from their perspective. This was something that we talked about. And the funny thing is with the same athlete, her quad strength is at 55% to 60% deficit, being this far out. And so in terms of this angle, again, not up to  mom or not up to the family to be able to figure this out. It’s there PT’s job. It should be something that should be caught there and to be pointed out. But the thing is, as I mentioned, it goes unnoticed all the time. We’re not necessarily trained in school to look at all this stuff. We’re trained to look at a few things. But especially from a movement quality standpoint and especially positions and angles, and especially from a performance standpoint, we just don’t learn this stuff in school. And with ACL rehab is such a nuanced rehab that you can’t just apply all the other scenarios and hoping that it would just translate over to ACL rehab, because it is just so different.

The thing is that the domino of this is that athletes will go on to play their sports with the same compensations and issues if it’s not addressed. Their performance suffers or potentially even like a reinjury can happen because this stuff wasn’t properly restored. And a lot of this is end up being, they just compensate. They either use the other leg, especially at higher speeds. That’s why a lot of contralateral injuries or the other ACL side can get injured because they go to sprint and then decelerate and they don’t have the ability to slow themselves down because they don’t have the strength or the power to do it, then therefore they have to figure out some sort of other way to do it. And that’s where the healthy leg comes in and can become an issue at that point. This is something that I want to make sure it stays on the radar. 

Now, what can you do about it? This is where the concept of capacity versus strategy comes up. I’ve talked about this a few times. Something that I learned from Eric Mira, but this is something that is super valuable, a great heuristic in order to understand, “What should I work on should I work on getting that shin forward? Or shall I work on strengthening? What you want to think about is this funnel and at the top of the funnel is capacity, and at the bottom of the funnel is strategy. We need to go through the pass through and check off the capacity box first, before we’re able to get to the bottom of the funnel, which is the strategy. Because no matter how much we train the position, we’re not going to get it the capacity or the strength is not there. Make sure that we need to train that first before you force the position and no matter how much, if I were to do this with her, she’s not going to get it because the quad strength isn’t there. And so then therefore she’ll continue to avoid it. Or maybe we might get lucky with some assisted positions, but then as soon as the strength is demanded or I take away the assistance or revert right back. This is time and time again with our ACLer we see this, if we don’t address the strength or whatever the deficits are. 

Now, this is assuming, pain, swelling, flexion, ankle dorsiflexion, or something else isn’t the limitation here. We’d assess for this. As I had mentioned before, I’ve had athletes where those have been the issue. We address the impairments, and then we work progressively on the skill of getting that positive shin angle once we can say the prerequisites are there, meaning do we have the flexion? Do we have the pain and swelling under control and really good? Do we have the ankle dorsiflexion there? Do we have the quad strength? That is so key. This is something that I want you guys to be able to put in play and you’re probably wondering like, well, what can I do about it? Or how can I even assess to see this? I’m going to give you some simple stuff to think about and look at, and of course, talk with this with your rehab provider or professional, you’re working with. Because the last thing you want to do is leave this unaddress. I promise you, it should rear its head with different things, whether you notice it or not. And it will be something that you want to address. 

A quick and dirty assessment, if you’re far enough along, just make sure you’re not like a week out. And make sure you’re not, at a point where it’s not worth doing the test or the assessment for it. But you can video yourself doing some walking lunges, some simple walking lunges from the side. And you’re going to take a look at your shin angle, does it match how the other side looks? If you have one side that’s been injured or the operated side, and the other side is the uninjured or  unoperated aside, you’re going to see essentially, what does that shin angle of that front leg look like? Is it neutral? Is it moving past your toes? And then can you move your knees past your toes without the heels coming off the ground? That’s going to be really important. Does the angle itself that shin and that knee moving forward match the other side or does it look different? Can you do it at least a few inches past your toes? These are all the things that we want to make sure we look for with that positive shin angle with a walking lunge assessment. You could even do it with any other movements that have the knee more involved. Even as something like a single-leg squat to box, although you can use your hips a lot more with that. I like a good walking lunge because it really just puts it out there. You don’t need to think about all right, dry my knees or my toes. 

Ideally, it’s just kind of like a blind test of do the thing and see what your body does. And so then therefore that allows us to look, can we get there? And if it looks different than we need to investigate, why, is it the ankle? Probably not, but in some situations it could be. Is it pain, swelling, maybe? Those are things we want to assess and see is pain my wall that I’m hitting? Or is swelling so puffy in there that it’s limiting my knee, being able to bend all the way and feel uncomfortable so I just want to keep it less bent? Is it the knee flexion itself? Do you have the range of motion to access that? It could be some other things you might be dealing with some sharpness around the kneecap, which comes back to pain. There could be some weird clicking that’s making you just like avoid the position or be fearful of it. There are surely some other things that could play into this. But a lot of times, if we go down this checklist, the last thing we’re going to look at is the quad strength. And I will put my money on it. Most of the time it is. This is something that literally, when we test people out, they will have deficits there. And it’s usually the rate limiter in most situations.

Once the athletes have a solid level of quad strength, we’re talking 70% symmetry, or really if we’re comparing to bodyweight, we want them to be at least around 2 Nm/kg or more. That is not a perfect number. But if you are in the low ones, it’s probably still going to be a problem. If you’re getting into the high ones of this compared to body weight, that is definitely a more tolerable. And then definitely in the two’s, you should be able to access that position a little bit better. Once we do have the quad strength up to a specific level like this, this starts to clean itself up. Sometimes naturally, a lot of the times too, though, we have to be intentional about training this from a technical aspect, the skill or the strategy to get the athlete familiar with accessing that position again. Their body has basically a race doing that and especially if you’d been working on this previously, just like this athlete example. They have been doing a lot of these lunges and positions without moving the knee forward. We’re actually having to take a step back. We’re actually having to train the quads and get the quads to up to a certain capacity or a threshold and then we’re going to work more on that positive shin angle. Can I embed some of that stuff in? Sure, we might do a split squat position with a knee drive forward target and hold that position. Or we might do a knee wall tap to get our knee over our toe a little bit more comfortably. But at the end of the day, we’re going to make sure we look through that funnel of like, all right, first pass through is going to be capacity or strength. And then second to that is going to be the strategy. Then we can start working on it. Because if we try to do the position first, but you don’t have access to it, that’s going to be a problem. It’s like me saying, like, I want to try and get my arm over my head. But when I go to passively lift your shoulder in your arm and I can only get it to 90 degrees. So think about it being parallel to the ground. It doesn’t matter what we do. We can’t get your arm overhead because we need to still access that position. No matter how much you work on the skill of getting your arm overhead, we got to work on getting access to that position first and then getting control in that, then we can work on trying to get overhead. We got to make sure that the capacity is there from range of motion to strength, and then we work on the skill of it first. 

This is something that I want to make sure you guys, when you walk away from this episode, you understand what I’m talking about with as positive shin angle or ways to look for it, ways to potentially ask your PT about it or your coach about it and understanding what are the limiters and what you can do about it. It’s something that’s so crucial from lifting to dynamic activities, it gets overlooked all of the time. And we’ve seen athletes who are six months, a year out, two years out, you name it. We’ve seen athletes all over the board with these same strategies where they don’t want to allow the knee to move forward. And a lot of times, it’s not just because of while they haven’t worked on it, it’s just more so of, they still don’t have the prerequisites there. And a lot of time it ends up coming back to quad strength. I’m not saying always. We have all the other things that we can look at and some things that we didn’t even mention. But I want to make sure that we talk about the prerequisites and understanding, well, can I go through this checklist and understand, is my ankle good? Is the pain good? Is swelling good? Is knee flexion good? And then let’s see how my quad strength is. This is something that the knee needs to be comfortable to do with the positive shin angle because you see it so much with all the different tasks that we do from just daily life to sport, to especially dynamic activities. 

Otherwise, what happens is that the stress goes other places. Because when you are asking the body to do something, it just figures out the way to do it. So that’s where it can be problematic because we want to spread that out appropriately, not only from a performance standpoint but most importantly, from an injury reduction standpoint. We want to make sure we don’t do this again. But then we also want to make sure we come back better than before. So that means addressing some of these issues from a qualitative standpoint, and making sure that we are dialing in these different buckets in order to make sure that when I’m doing positions like this, do I look the same side to side? Can I drive my knee or my toe the same way? Do I feel comfortable loading it this way? I promise you, it will be a massive game-changer in your rehab and especially in the way that you perform and the way that you feel. 

I hope this is helpful, guys. If you have any questions about this, if you have videos of you doing this and you want me to share some feedback for you? Send them over to me via my email at ravi@theaclathlete.com. I’ll be happy to look at it and send you just some thoughts. You might need to provide a little bit more context with this. Ideally, send it to me over on Instagram that’s a little bit easier (ravipatel.dpt). But this is something that I think is very crucial, something that is important for us to make sure that you guys are very well aware of. Doesn’t get talked about a lot in this space, but especially coming from a performance background, this is something that I see all of the time. I hope that this can be helpful in your own ACL rehab. Until next time, team. This is your host, Ravi Patel, signing off.