Episode 46 | Strength Testing in ACL Rehab – Part 1: The Problem

What’s up guys, and welcome back to the recording studio for the ACL Athlete Podcast (aka my kitchen counter). And just a heads up, construction is a madhouse today. My wife and I live right next to all this construction that is going on. And there’s leaf blowers, there’s dump trucks, you might be able to hear something backing up right now. Just think of it as some good background music as we talk today. We are focused on strength testing in ACL rehab. And this is a particular topic that I am super excited to talk about. Today, we are focusing on part one, which is the problem. And next week we will dive into part two, which is the solution, as you can imagine. And while it’s not simple, there are things we can do to help in this area and in ACL rehab to make sure we are tracking our strengths.

And I think one thing you can see, especially on social media, which is where a lot of people go to get their information or maybe Google or something like that, and you start talking about strength testing, especially in ACL rehab and you just get this whole slew of information, it’s kind of vague. There’s not really a lot of information directly about how to do it, and it’s not very practical. It’s either people who have really good access to equipment and resources, are able to get their strength tested, or they’re just kind of left to maybe just try to figure things out. And this all comes back to a system-related issue of the way that we do ACL rehab, especially in the U.S. And I know that this is also very international based, where it’s a high population in terms of, there’s over 200,000 to 300,000 people every single year. And this is just in the U.S. alone, who are getting ACL injuries and going on to have ACL reconstruction.

And so with that, we need to build a system that is going to serve this population, and it’s not just something that’s knee pain. This is a very long process that we’re talking about anywhere from 9 to 12 months. We need to serve these people and serve you guys who are listening. This is where strength testing is going to be really important. And I want to give you guys some practical solutions to be able to test your strength. And that way you’re not left in the dark in case the rehab professional you’re working with is not worried about it or not assessing it appropriately. And you’re going to see here today in the conversation about the problem that it’s so important to test. And I think there needs to be practical solutions for any of you out there to be able to do this. And that is my goal with this two-part series. And also, if you track on Instagram, there will be a lot more practical information from a visual aspect. If you’re not following that, my Instagram is at ravipatel.dpt. And that’s where I’m going to be posting some information, some you’ll hear on this podcast. But then there will also be things that you will see that you can utilize today if you need to test your strength.

Today, we are talking about the big-picture problem regarding strength testing in ACL rehab. The way that we’re going to start this is by talking about some statistics because I think we need to anchor this, and I think we need to realize where we are so far and how we are doing. And so we’re going to start with re-injury rates. And to preface all of this, my goal here is not to be negative and not to be down on how bad things are. But we also don’t need to dance around these things and act like, oh, ACL rehab is just this shoulder pain that we’re trying to get better; it’s actually a big problem. And this is going to highlight some things from research and just statistics, that are the facts out there to the current day.

Let’s talk about re-injury rates and statistics. We’re going to talk through some facts here and then we’re going to make our way down. Grindem et al. in 2016, reported 33% of players who returned to sport with an LSI of less than 90% sustained another knee injury over the next two years upon their return to sport. Whereas only 12% sustained another knee injury over two years. LSI is limb symmetry index; and that’s comparing our involved ACL-injured side to our uninvolved, non-injured side. And so the goal is to try and get close to 90% of that limb. If we’re less than that, then there’s a 33% chance of an increase in re-injury within two years. And so that same study looked at a significant decrease in re-injury risk when athletes waited at least nine months and passes greater than 90% limb symmetry on quad strength and hop tests.

Here, we see that limb symmetry comes in again. And also waiting till nine months, which tons of studies show us that nine months seems to be a sweet spot. It’s always going to depend on each person’s case. But nine months is a very good, sweet spot, as a starting date for a return to sport. Paterno and company reported 30% of athletes suffered a second ACL injury within two years of returning to sport. Wiggins, 2016, a 23% retear rate in athletes less than 25 years old, so we’re talking about a younger population. Typically, 15% of those are on the same side as the initial ACL injury; 7% of those are on the other side of the ACL injury. And what we also see typically is that with males, it’s the same side, and with females, it’s the opposite side. Not always the case, but that is something that we do see in some of the research. Last one here, Kyritsis and company in 2016, showed athletes who did not meet the discharge criteria before returning to professional sport had a four times greater risk of sustaining an ACL graft rupture compared to those who met all six return-to-sport criteria. In addition, hamstring-to-quadriceps strength ratio deficits were associated with an increased risk of ACL graft rupture. I know a lot of you listening right now are probably like, why is Ravi sticking a knife in and twisting it? But just follow me here. 

Return to sports rates, Ardern in 2011, reported 33% of athletes returning to sports within one year after surgery. That’s one in three athletes returning within one year to their sport. Ardern in 2014, said that only 55% returned to their competitive level of sport. And this is a really good study because it really gives you a good visual of, okay, how many people return to the same level or not. This is a part of it, 81% of athletes return to some sort of sports, 65% return to pre-injury level of sports activity. But only 55% return to competitive sports level. So that’s about half of the people. One of the things with this, I want you guys to think about, is that if you’re having a long process and it’s taking more than six months, more than nine months, more than a year, just know that the research shows that. It shows people not necessarily getting back to those levels, and it’s only a lower percentage of those people who do. And so that’s where this is a problem. And to kind of take this home, Toale et al., in 2021, this year, reported 28% of people don’t return due to a fear of re-injury. And we know that there’s such a huge psychological aspect and a mental aspect to this. It’s so big. I went through it with my own two ACL surgeries and that is big. I know a lot of you out there are also dealing with this. Just know that this is shown not only in your own personal experience, but we’re seeing this in the research and in the data that’s being collected. 

We have to ask, why are these rates not so great? Why are they bad? This is not an easy question to answer. And it’s why we’re also continuing to see more and more ACL injuries and people not getting back to sports. There are a lot of factors at play. But when we look at this research and we’re looking at these outcomes versus people who do well and who don’t. A lot of it comes down to the criteria or these standards that they need to meet to be able to get back to certain things in life and sport. And that’s via a testing battery. We talk about clinical tests, we talk about performance tests, strength testing. There are a lot of things that go into this for a testing battery. And depending on who you’re working with and whether they’re up to date on things or whether they have the time or whatever it is, a lot of times you don’t see a testing battery being implemented, or maybe people just fall off rehab and never get this in place. 

And then it comes down to, well, is that testing that you’re doing periodically through this process going to inform your rehab and your strength and conditioning and training program to be able to test, intervene with these programs and then retest again and making sure that we’re progressing along this path. And so testing plays a huge role here, so that way we know exactly where you are at, where athletes are at, and that way we are able to know, okay, this is what we need to do to hit these specific criteria by the time you return to sport or return to run, or whatever it is that we’re trying to get back to. 

Then let’s see the stats when we do the test. Webster & Hewitt, in 2019, reported passing return to sport test batteries resulting in a 60% reduction in risk for graft rupture on the ipsilateral side. So that’s the same side of the ACL injury. And then there’s a significant decrease in re-injury risk when the athlete waits at least nine months and passes 90% or greater limb symmetry on quad strength and hop testing, which we talked about earlier by Grindem in 2016. These are things that are highlighting, okay, if we do meet these tests, then our risk of re-injury goes down. And then also we have much more success in terms of our return to sport; high return to sport low re-injury risk. And when we break apart this testing battery, one of the big components that you see is strength testing. We’re going to zoom in specifically on this because it has such a big impact on it. Let’s see what the research says on strength testing. And specifically, we’re going to talk about some quadricep strength testing in ACL rehab. And just so you guys know, I touched on this in a previous podcast: the most important muscle in ACL rehab is the quadriceps. No arguing here. It is the quadricep until it’s not the quadricep. Go check that out if you haven’t already. But this is where we’re going to see how it really impacts everything. 

A big one by Lepley, in 2015, overwhelming evidence links quadriceps strength with essential outcomes. Your normal walking and running patterns are just general knee functions. Our self-reported success return to sports levels, subsequent knee injuries, and long-term progression of knee osteoarthritis, which I know can be a big concern with people. Iwame, this year, reported on running and saw that quadricep strength to body weight ratio is a significant indicator for initiating jogging after ACL reconstruction. When we look at the performance side of things, Chaput, in 2021, this year, when they looked at quadricep strength versus hop testing to give some input about this questionnaire that they had. The quadriceps strength testing gave so much more information in terms of the variants and the scores as compared to the hop testing didn’t give nearly as much to the patient function. 

Last one here, quad strength was a good predictor of function and performance on hop tests. More specifically, patients with less than 85% quad strength so that’s the LSI we’re comparing, demonstrated decreased function and poor performance on hop tests. Important to note that these findings were the same regardless of the graft type, the presence of meniscal injury, and knee pain or symptoms; that’s by Schmitt in 2012. You guys get my point here.

Strength testing is really important, especially for the quadriceps; it’s so important. And my goal is to bring this to light. And if you take the collective body of ACL research and the most commonly reported and researched impairment is a significant decrease in quad strength. You read most studies if they’re measuring it and they’re tying it to outcomes, it’s typically something related to quad strength as well as other factors (don’t get me wrong here). But it’s a big component and it’s a big foundation of this process, as well as other strength measures like the hamstrings and glutes and calves. But these are going to be really important. And most of all, the quadriceps is at the top of that in priority and importance here. And this is something that I just kind of want to point out because these studies report these findings. And when you summarize it, decreased quadricep strength is a great predictor of decreased function after ACL reconstruction. Quad strength is so important and so our research, then objective strength testing to assess the strength of the quad is a must for good outcomes in ACL rehab and return to sport.

Some practical ways to think about this is that the quadriceps is essentially weak until proven otherwise via objective testing. Not just kicking into your physical therapist’s hand, at your ankle, and they say, okay, it’s strong enough. No, we need to have numbers associated with each side and see how do they compare. And when I think about this with the athletes that I work with remotely, seeing them move and then also in the clinic, it really does show, from a just anecdote and from a clinical perspective. When people come in, the quadriceps are atrophied. They get smaller right after ACL injury and surgery. They have a hard time activating. The goal is to try and get that to kick back up with their range of motion. But then they start to avoid loading the knee because of the pain and because of the weakness. And we start to see that with different mechanics. 

Let’s say for example, they start to squat, you’ll start to see people shoot their butt back into a hip strategy is what we call, to be able to load more of their glutes and their hamstrings as opposed to loading their quadriceps and their knee because of the weakness and the pain. Maybe it’s just a motor pattern that they learned right after ACL injury, or as they are starting to get back into movement. And that’s where the coach and the PT, who you’re working with, it’s going to be important for them. To, one, emphasize making sure the knee moves forward, and it’s okay to load the quad and the knee and not adopting these types of strategies. And then when we see this into more dynamic work, if you will, talking about changing direction, cutting, doing some jumping, any type of stuff that we’re more so focused on. Even in running, we see this translate over.

Research shows that quadricep weakness starts to impact our ability to use more of our hip and more of our hamstrings and glutes as opposed to our quadriceps in our knee. And then you’ll see this strategy over and over and over, even in hop testing. What typically is done with a hop test is that we measure the distance from side to side of someone doing, like let’s say a crossover hop or a triple hop, whatever it is. And we see, okay, is this the same distance? But then, one of the things we need to make sure we focus on is not only that number, the comparison side to side, and how did the athlete achieve via loading the knee and the quad, or was this more so of shooting the butt back and keeping that tibial or shin vertical?

Then we’re like, okay, maybe they are still avoiding the knee strategy or the quadriceps, and then we have to ask why, is it a motor control issue? Is it a weakness issue? And a lot of times what ends up happening is that it comes down to a weakness issue. Maybe the athlete does not have eccentric control of the quadriceps. Maybe it just doesn’t have a high force output to take on the loads with those types of activities. There are a lot of questions and the only way to answer those questions is to test, to be able to know from an objective standpoint, what is that number and how do we compare side to side, as well as relative to your own body weight. To quote the great Eric Mira, because he’s way smarter than me, “It’s the quads until it’s not the quads.” And today, the emphasis is on strength testing. And we’ve highlighted some statistics to show us why re-injury rates are so high, why are return to sport rates so low, and then also how does testing, specifically strength testing play into this. 

And the last thing that I want to talk about here, is talking about a study that was done by Greenberg in 2018. And this is basically asking, when we do tests in ACL rehab with physical therapists, what are we testing, how are we doing it, and what does it look like practically versus what the research is doing? And this is such a good way to highlight the problem because I think what happens, is we highlight a lot of the clinical research and it ends up being in a specific population. But now we need to translate this to the general population, anyone who’s kind of going through ACL rehab, and then also what is actually happening in these clinics where people are going through this process. And so that’s where this study comes into play. And it was a physical therapist survey, essentially the way that we’re currently testing strength and other measures in ACL rehab specifically. 

And there’s also a good article highlighting this by Zach Lentini from the JOSPT blog called “Living in the Stone Age: Why Are We Still Testing Strength With Our Hands?” That’s a really good article and I’m actually going to link that in the show notes. Because it’s just something that’s really short, really helps to stand out on how we are actually testing strength specifically. But if we dive into this study by Greenberg in 2018, this survey of 1,074 physical therapists in the U.S.; 53% of these physical therapists were certified sports or orthopedic specialists. And when we look at the testing that they did for testing strength in this survey. Of those who relied on MMT to begin modified sports activity; 56% reported using MMT as their only means of strength assessment, while the remaining 43%-44% used it in conjunction with more objective measures. And for you guys listening and MMT is called a manual muscle test. And while there is some value in it, it does not test strength. It only lets us know if a muscle is active or not, realistically. 

And there’s some research to show that it’s good in older geriatric populations and neurological conditions. But to test strength, specifically an MMT and specifically in this case, it’s where a physical therapist will take their hand and they will try to stabilize the top of your knee. You’re sitting on a treatment table or a chair. And they’ll take their hand and they’ll put it at your ankle and they’ll ask you to kick out into it as hard as you can. And they’re going to try and assess your strength, and then they’ll try the other side. They may do it to the back of your ankle to assess and see how your hamstring strength is. And it’s not really an assessment or a test for strength. It’s really just letting us know if that muscle is active or not; that basically it. And they created a number scale to be able to show, okay, is it weak, slightly weak, strong, really strong. 

And it’s very subjective. It’s going to be very different relative to each person. Because one, if I have an NFL alignment in front of me kicking out into my hand, you best believe I’m not going to be able to hold that. And then comparing that to someone else who is maybe a hundred pounds and not very strong, then that’s going to be a very different feel of what force you’re putting in. And every time you try to put force in, you can also apply different forces. And so it’s so subjective. There are no numbers really attached to it that are true and honest, which is why this is such a huge problem. And for 56% of physical therapists to assess strength that way as their means to start beginning modified sports activity so that could be maybe like jumping or running or cutting or anything of that nature. Using your hand as a strength measure is just not going to do it; it’s subjective; and it’s going to vary from person to person. We need something that is going to be true and honest and with a number that is associated, that is not subjective. 

The other thing to highlight here is that 53% of this group, of the 1,074 that was tested, were certified sports specialist or clinical orthopedic specialists. In reality, when we look at our population in the U.S., that’s really only 12% of the physical therapists that exist in outpatient physical therapy. This survey probably overestimated the use of good objective strength assessment and underestimated the reliance on MMTs. Even though it’s 56%, that number is probably higher because of just the whole population in general that are certified sports specialists or orthopedic specialists versus not.

Guys, this hurts my heart more than anything. I hear athletes every week talking about coming from a different physical therapist or a different healthcare professional. And when I ask them if they’ve been tested for any type of measures, specifically strength, their answer is typically no, or maybe they’ll say yes. And then when I ask how they did it, they will say, I kicked into their hand and they said my strength was good. I’ll even see surgeons do that, and it really does baffle me that we’re okay with letting that be the measure of strength. And then we go on to see these re-injury rates and return to sport rates and are wondering why it looks that way.

At the end of Zach’s article, he says, “If you suspect that your patient is weak, prove it with objective testing. If you are declaring your athlete ready to return to sport, you better have the data to back it up.” And I 100% agree. And then one thing that I want to take a step back from and ask, well, why are we seeing this? Why? Not just be like, okay, this is the data and this is what it is. It’s like, well, let’s take a step back and see why are we seeing this. While there are different factors at play, it comes down to laziness, time, lack of resources, lack of knowledge, maybe insurance.

All of these things are going to play a factor into this. And the thing about this MMT test is that it’s doing more harm than good. And the reason I say this is because if we test this way, it gives us false thinking and confidence with a false assumption or a “number ” that we have, like a strong test, if you will, when someone kicks into my hand. It makes you think the athlete is strong or capable of doing this. And that makes you start to intervene in ways that you have a false confidence of a strength of this specific athlete. And that does more harm than not testing it at all in reality because you’re operating under a false assumption at the end of the day. And that is just not going to be good, and it’s going to put this athlete at risk more than anything. Because you’re probably going to start doing things like hopping and cutting and more dynamic stuff, which requires more strength, which requires more power, which requires more elasticity.

And so then that’s going to be something that is going to be coming to a halt, and it’ll be noticeable from biomechanics and a qualitative standpoint. Why is this so important? It’s tied to the outcomes guys. It’s tied to the return to sport rates, it’s tied to the re-injury rates, ‘it’s tied to people’s mental health, it’s tied to a lot of different things that are going to impact the overall outcome and health of your ACL athletes out there. 

One thing I want you to imagine is that you’ve been told you’re getting a raise. And then when you go to ask your boss how much of a raise you’re going to get, they’re just like, you’re getting a raise. We don’t have a number. We don’t have a percentage, we don’t have anything. They’re just like, you’re getting a raise. Well, that’s cool, but like how much of the raise am I getting? Am I getting enough to be able to move into a different home, buy something new that I want for my family, is it something where it is just, you know, a few dollars here or there? It’s going to be important to be able to know a number specifically for that. Now, carry that over to your strength, imagine you’re told you’re getting stronger when you ask how much. They’re just like, you’re getting stronger. Great, well, where does this help to anchor me relative to the point of where I want to run, where I want to jump, where I want to cut, where I want to get back to the sport that I love to do, where am I at in regards to that? That’s the question that we need to be asking, okay, you’re getting stronger. But then with a number tell us how strong are we getting. And that’s going to be so important in this situation and to make sure we’re getting our strength tested. 

Now, the last thing to finish up here is: why isn’t there widespread testing? And if we go back to some of those things that I mentioned earlier, time insurance doesn’t cover it, laziness, lack of resources, lack of knowledge. Well, if we’re attacking these things, insurance doesn’t cover it. So that’s the problem. We can’t let insurance dictate everything we do, which is re-injury rates are so high and people get terrible care. 

And let’s be completely transparent here. If someone goes on for re-injury, if you’re a clinician out there, would you be proud to say you did all you could in your power to make sure that this athlete was set up the best to be able to return to sport? And if the answer is yes, then that’s awesome. If not, then you got to ask yourself why.

And if insurance is really driving this, then there needs to be some sort of reflection on this to make sure we are capitalizing on this and it really should be a part of this. We are always assessing outcome measures in physical therapy, insurance or not, this should be a part of it. 

If laziness, well, that’s just a you problem in all honesty. Sorry guys, I’m fired up. But this is a serious matter. If it’s laziness, then you got to reflect on that and just ask, okay, well, am I okay with someone getting re-injured or having a terrible quality of life? If you can live with that, then great. And then if we’re talking about time, this does not take very long to test. We don’t need this fancy equipment. Will it be good? Sure. But there are measures that we can use to be able to access this without having to take too much time or even expenses. This can take anywhere from 5 to 10 minutes max, and it will do a world of a difference with the interventions that you place and use for your ACL athletes and clinicians out there. It’ll give you so much feedback and that’s where it’s going to be really important. 

If we talk about lack of resources, there are cost-effective solutions out there. Every clinic that exists can spend anywhere from $100 to $200, at a minimum, to buy something to test strength. And what will usually come up is that they argue that they can’t afford the cost of a handheld dynamometer, which we’ll talk about in the next episode. But they’re buying lasers that are thousands of dollars, ultrasound units that are thousands of dollars, dry needling courses, all of these things that, in all honesty, don’t really have that much research to support it. And yet there’s thousands being thrown at it. And then when we do have something that the research, science, and everything supports, we can’t throw a few hundred bucks at it. And so this is essentially a call to action of like, “Hey, let’s do something about this.” And if you’re an ACL athlete listening to this, we need to make sure that you get tested. And if you’re not, then figure out a physical therapist that you can get tested. If they’re not going to help you, then find someone else nearby to you. And if they’re not going to help you, then please reach out to me. 

And my goal with this podcast, and my goal with this platform, with the ACL athlete, is to make sure that any of you athletes out there don’t go underserved and that you get good care, and that you don’t fall through the cracks. I want to make sure that you get served, so please reach out to me. With this next episode which is going to be focused on solutions, I don’t want to sit here and just complain about here are the statistics, and here are the issues. Let’s talk about some solutions that are practical and that people can use today, that the next episode will focus on. I plan to address this knowledge gap and educate, and to make sure you’re doing it right and doing it well and it’s affordable, that is very time limited. And that way you can’t let laziness or insurance or lack of resources really be an excuse.

I’m going to end this here because I need to and because I could just keep talking about this for days and I’m really fired up right now. I’m just going to go work with some of my ACL athletes and put that toward them. I appreciate you all so much for listening, for all the messages, for anyone who reaches out, it really means the world to me. And we are going to make a change in this space. And I hope that this gives you something to be able to look forward to and to know that there are things out there that are looking to the positive and trying to help ACL athletes out there, get the best care and get the best information to know that they are in good hands.

That’s going to be it for today, guys. Please tune in next week for the solutions podcast. I think is going to be a really big podcast. And I want this to be able to reach as many people as possible, so they know that there are options besides just having to go to these $50,000 machines or these clinics and being like, okay, I could spend a hundred bucks and realistically get these that I need to. And I’m going to walk you guys through it, just as easy how to do it and different ways to do it, even if you don’t have those resources at hand.

All right guys, I’m signing off, until next week. Love you all.