Curious Conversations, a Research Podcast

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Travis

We have reached what many people consider to be the most wonderful time of the year.

And course I basketball season. And like most basketball seasons, it'll only be a matter of time until a player from one of my favorite teams goes down with some sort of injury. One of the most common injuries in basketball and many other sports are knee injuries, specifically ACL injuries. And even though I have had an ACL injury, there's still a lot I don't know about the ligament, how you injure it, and how you recover from it.

But thankfully Virginia Tech's Robin Queen is an expert in this very subject. Robin is the L. Preston Wade Professor of Engineering in the Department of Biomedical Engineering and Mechanics and the Director of the Kevin B. Granada Biomechanics Lab at Virginia Tech.

Her research focuses on the whole body mechanics with an emphasis on load symmetry and functional outcomes following surgical interventions. So Robin was kind enough to explain to me what an ACL does, how we most often injure our ACLs, and maybe most importantly, what should we do to best recover when we have an injury? We also talked about whether or not we're seeing more ACL injuries currently in our young population, as well as what coaches, parents, and even the athletes themselves can do to preventively mitigate either that initial injury or a secondary injury post-recovery. Wynne Chi also gave some practical advice on how us, let's just say seasoned athletes, can best take care of ourselves as well. I'm Travis Williams and this is Virginia Tech's Curious Conversations.

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Travis

I thought maybe just a good place to start this conversation is simply, what is an ACL and what does it do? Because I know I've had an ACL injury, so I'm very familiar with it, but maybe a lot of people don't. Maybe they hear about these things when they're watching a game on TV or something and they're like, I don't even know what just happened to you. So what is it and what does it do?

Robin

Now, it's a great question. think, like you said, we're very used to hearing it in popular culture. so the ACL is the anterior cruciate ligament. It's a ligament within the knee. And what it does is it resists the movement of the lower part of your leg going forward. Right? So when you're running or cutting and you stop quickly, it's one of the, it's the ligament that's inside the knee that keeps the knee and the lower leg from moving forward. And so it's there to, what we say is resist anterior TBL translation if you want to go with the medical terms for it, but it's there to stabilize the knee and that's at school.

Travis

And so I know that's one of your areas of expertise, one of the areas you research a lot is how to prevent re-injuries. But I guess I'm just kind of curious when it comes to injuries in human beings, how do you go about researching that? Because I don't assume that you can do a lot of live tests on me to see how far I can push it. Or maybe you can. I don't really know. So how do you go about researching it?

Robin

Again, another great question. think there are different ways that we think about sort of pushing human performance as well as kind of the injury prevention side. A lot of the work that we specifically do is focused on the biomechanics. I'm looking at the way somebody is moving. There's also the exercise physiology piece, which is another component. And certainly I have amazing colleagues that do that work. But for us, it's about how does the human body respond to different things. And so often what we're doing is putting people through different sets of activities to see how they're going to respond to them. So if we're talking about prevention of maybe the first injury, we would do a specific set of tasks that we know tend to be related to the mechanism of injury. So they are similar movements to how somebody would get hurt. And what we want to do is understand are there differences often between men and women is one question that we ask.

But also as you go through growth and development, do we see a difference in the way you respond to those situations? And so for us, it really is like you would imagine. We try and create as best as we can a scenario that looks like something somebody would experience in sport. So lots of cutting, lots of jumping and landing, lots of changes of direction, especially when we're talking about the ACL. We can't always create the exact same environment. Obviously, we're in a lab setting usually, but with the technology advances we have now, we're getting closer and closer to being able to do this work in what we would consider game-like scenarios. We can't necessarily test in-game because it would require technology that most officials wouldn't let us use in a game setting, but we can certainly begin to look at some of these movements in live practice and things that are similar to that or scenarios again that we set up hopefully as close to the end goal as we can get.

Travis

Well, I'm curious, just what are some general, common ways that folks injure their ACLs and maybe what are some, what do those injuries look like?

Robin

So typically the injury is going to happen with a rapid change of direction. So that can mean different things. Cutting is one way, right? So you plant and then you change direction, either go left or go right off of that planted limb. The other way that it often happens is landing from a jump. So if you're playing basketball and you have to grab a rebound and you come down and you land a little awkwardly, that's the other mechanism that we often see happen with our ACL injuries. I use basketball, it certainly happens in soccer and other sports. But it's really anything that is requiring a rapid change of direction is the most common mechanism for injury. Certainly there are people who have what are called contact injuries. So what I described to you is a non-contact injury. And that is the majority of ACL injuries are non-contact. There are contact injuries which would be somebody hitting the knee. So if you're about football and you get tackled and hit the knee itself, that can also cause an ACL tear, often also tears some of the other ligaments in the knee. So ACL tears are interesting because they're not usually what we term as isolated. They can be, and it can just be the ACL. Often we will see an ACL tear and then sometimes a meniscal tear. So the meniscus sits and kind of covers the knee joint and as a shock absorber. And so what we would often see is also a meniscal tear. Sometimes that gets fixed, sometimes it's not bad enough to fix and they just leave it. You certainly can go to the extreme where you have what we call a multi ligamentous injury. And so more than one of the ligaments in the knee gets torn at the same time. We don't, in my research, aren't necessarily focused on the multi ligament injury space because they tend to be more traumatic injuries.

Travis

Yeah, I think I can very vividly remember a couple of people that had multiple ligament injuries. Not that I know personally, but I just saw like during games and it was like everything came to a grinding halt. Well, you mentioned you mentioned young people. Is that the group that experiences the most ACL injury?

Robin

The majority of non-contact injuries happen between about the ages of 14 and it depends on the study you read, either 18 or 21. And so it really is a younger, sort of adolescent population.

Travis

Do we know why that is? Is it just they're more active or?

Robin

we don’t have a definitive answer on that. We know, interestingly, that women are more likely to tear their ACL than men. It's about four to eight times, again, depending on the study. So there's been a lot of theories over the years as to why some of that, the theories have been it's hormone related, it's sort of the way the body is morphologically shaped is another one. So hip width knee angles, things like that, people have thought played a role. Some has been related to questions of strength. And honestly, I don't know that we've gotten to a point where we can give a definitive, like, this is why somebody gets injured the first time. There's a whole lot of razor jar there in really detailed down to the slope of the tibia, which is one of the bones in the lower part of the leg and the angle of that slope and how does that play a role. so there's been a lot of theories. We haven't found sort of the golden ticket to like, this is how we prevent ACL injuries. And so I think that's still for a lot of my colleagues, a major area of research. We've done a little bit of that, but again, my interest has really been in sort of the return to sports space where we're looking at how do we keep people from getting hurt when they go back again.

Travis

Yeah, well, I am am curious. Are we are we seeing more ACL injuries now than maybe we have in the past? Or do I just watch more TV? Are they just covered more?

Robin

I I think that the numbers, if we look at them from an epidemiology perspective, are about comparable to what they've always been. I think you're starting to see some, potentially see it more in your high profile athletes than maybe we have in the past. But there's about the same numbers, which is not what we want obviously. We want to see the numbers decrease and not going up or not even staying consistent. I'm not sure that there are really more of them. I think we just are starting to be more aware of them. We're talking about them more. And again, you're seeing them in high profile athletes and then they're starting to talk a little bit more about, how long are they going to be out? As a result, it's starting to become more of the conversation than maybe it had been in the past. And again, most of your professional athletes are slightly outside of the range where we would consider them at the highest risk. They're not typically your 14 to 21 year olds. So that's part of it, right? It's a little bit of a different age group that we're starting to see. so some questions about why, right? That certainly can be an area for people to be able to ask more questions.

Travis

Yeah, I was curious because I know athletes are, at least from what I understand, bigger and faster and stronger all the time. And I'm just curious to how that impacts these type of injuries.

Robin

From the research side, from what we know from the literature, I don't know that there's anything definitive on that space, right? In terms of bigger, stronger, faster, sports performance based indicators of increased risk. Certainly we know that there's increased risks and we've talked a little bit about this before for the questions of early sports specialization and that placing people at greater risk. So there may be some aspects of movement asymmetry, so one side moving a little bit different than the other, that are starting earlier because they are specializing earlier and they're not having as many different types of experiences as they once did. So again, I think there's a lot of questions that remain unanswered in terms of why are we seeing this maybe more in our more elite athletes at kind of a little bit later age.

There's also, it goes back to the second injury piece. In a lot of those cases, we don't know whether this is their first or their second. So we just are told they had an ACL injury. So it could easily have been a second injury or an injury to the other limb. And they had one prior on the other side when they were in college or when they were in high school. there's a lot that kind of plays into that into the question of what a bigger, stronger, faster in and of itself is doing this, or is it something different about the way we're training our younger athletes as they progress into those more elite spaces?

Travis

Yeah, maybe it's more of a sports culture type issue than it is just a physical issue.

Robin

And there's certainly equipment questions that people bring up in terms of footwear. There's lots of, there's been lots of debate, especially in soccer on, on footwear and how that plays potentially plays a role in injury risk. That's some great work that's come out of different places. The most recent one was out of the University of Oregon where they were looking at female specific soccer cleats with the goal of trying to reduce injury risk in, in female sports. So there's an interplay right between the equipment that we have and that we use and the way that we move. And so those certainly can play a part.

Travis

Yeah, that makes a lot of sense to me just completely anecdotally because when I hurt my knee and then I went back and tried to play basketball is how I hurt my knee. But I remember I changed, I started paying a lot of attention to how heavy the shoes were that I was wearing. So that does make a lot of sense to me. I know that's your real area of expertise is that prevention, recovery and prevention of the second injury or another injury, I guess I should say. How often does somebody end up having another injury after an ACL.

Robin

I wish again there was a definitive answer on that. literature is kind of a range. Somewhere around 30 % is kind of the average. The caveat for that though is that that is 30 % of those who return to sport. And so we know that there's a large number of people that after the injury don't go back to sport or don't go back to sport at the same level that they were playing prior to the first injury.

So we call it 30 % as the number because that is what the literature has shown us. The numbers are probably slightly higher if you account for the fact that not everybody's going back, right? So if you assume that a certain percentage aren't going back into sport, we don't know whether they would have re-injured or not because they're not being put into the situation.

It's a decent number of people and I guess I should be clear that when we say a second injury we're talking about either a tear of the graft, the one that was already fixed surgically, or the other knee. And so we talk about both as a second injury because that number is about 50-50 as to whether you're going to tear the graft or the other side, the other knee.

Travis

Is that just from like overcompensating?

Robin

That's my theory on it. think there are different opinions on that. A lot of what we have focused on over the years is understanding side-to-side symmetry. So how is the reconstructed limb behaving as compared to the other side? Not to say that the other side is perfect, because obviously there was some movement deficit that existed that caused the first injury. But what the literature has shown us, at least in small-scale studies, is that an asymmetry between the two limbs is a large predictor of somebody having a second injury. And so what we see often is that in thinking about the amount of force that goes through the leg is the easiest way to think about this. There's certainly joint mechanics differences, but if you think just about the amount of weight or load that goes through each limb, what we see very consistently is that following surgery, even out to two plus years following, they don't load the one that's been injured and they tend to put more of the weight and the force through the non-injured limb if it's a bilateral task. So if you're landing on both feet, we tend to see a much higher force placed on the limb that did not get injured than the one that's been reconstructed. So that's a lot of why we think that the previously non-injured limb is the one that's getting hurt is because they're overloading that side and it's taking on more than it's supposed to. On the other hand, there's the other side that's been reconstructed and because they haven't been loading it, often we believe that that injury, that second injury happens because they're then put in a position where that knee has to do something that it hasn't been trained to do because they've been utilizing the other limb. Right? And so our goals are often about, you know, how close can we get them to each other? but not simply by making one better, but by making them both better and then getting the one that's been reconstructed up to that higher, that sort of higher level where we know that they're doing what they need to do to be safe going back. And so I use load as an example, the way the joint is moving, 100 % plays a role in all of this, but the load piece is easier to explain and understand. As you can see, just...

And watching somebody stand there, they'll even stand differently and overload one side versus the other.

Travis

Yeah, I just had a conversation yesterday with my chiropractor about symmetry in my hips because things were not going well and he was going to try to fix them. Apparently I had a leg that was like longer than the other one or maybe I still do. I don't know. He did a lot of pulling and stuff and then he was like, I think it's better now.

Robin

Yes, leg length inequalities play a role in a lot of this and sometimes they're true leg length inequalities, which means that he could pull as long as he wanted and it would never be the same. And then some of them are what we call functional leg length inequalities, which means that something's going on in your pelvis and in your legs that is making it look like one is longer or shorter than the other.

Travis

he was probably doing some adjustments to try and make them seem similar or be similar again was the goal and to make it so that when I sleep it doesn't hurt because I've reached the age where that's a thing. And I think that this all started because I slept wrong.

Robin

Yeah, getting older is one of those things. It's not great for things like that.

Travis

When we talk about recovery and trying to prevent a re-injury, what are some keys to recovering well? I how long should we expect it to take and what should we be doing?

Robin

People don't love my answer on this one because everybody wants to get back as quickly as they can. get that. Literature is very clear and all of our studies are very clear that the earliest really is nine months. We will push you farther than that if we need to. So it's about how well you're moving and how comfortable you are with it. We haven't talked much about it but some of our work has started to focus on psychological components to recovering. So thinking about fear and apprehension, specifically if you're related to a second injury, right? So are you nervous? Are you scared about going back in? What does that look like? How is that then impacting the way that you're moving? Because maybe you don't think the knee is as stable as it should be. So there could be a lot of reasons for the fear and apprehension, but a lot of what we're struggling to, not just us you know, the field is starting to think about us, what is the interconnectedness between the movement mechanics that we've all been so focused on and some of these psychological metrics, again, of fear and apprehension, we again use a very big word called kinesiophobia for fear of movement. And that's been a growing area within the field for probably the last five to six years, is just trying to blend these two worlds together. So

When I say, you know, there's no definitive timeline because each patient is a little bit different. depends on your surgeon ultimately and the PT that you're seeing when they will release. But typically we're pushing nine months or more, which is different than when I first started my career where, know, at six months we were releasing almost everyone. I think the work that we all have done over the years is sort of shown that they're not really ready at six months. I'm not sure that everybody's ready at nine months. And again, we could get into the political pieces of like, how many PT visits do you have? And how long do you have to recover? what like, what does that mean? by political, just mean in terms of like, insurance coverage for going into rehab, I'm doing that work. So, you know, it's, it's tough, because it is a long process and again, these are younger athletes who are excited to get back into sport. So we're starting to see a decent number of them returning before the surgeon has actually cleared them to go back. And so that's another component is how do we get and continue to explain to people the importance of being really ready to go back and what the long-term implications are. So the other piece that I don't like to bring up to young athletes because they don't usually think this far down the line. And I hate to say it to you, I know you've had an ACL clear, but we know that in about, again, 10 to 15 years following your ACL reconstruction, you'll start to have early signs of osteoarthritis. And so if you look down the line, what that often means is you'll be having, or at least starting to have the conversation about a joint replacement. in your mid forties to early fifties, which is a lot earlier than we typically want to replace a joint because we know again, it has a lifespan in terms of the joint replacement itself. that's why for me, the goal is kinetic. I mean, obviously we'd like to prevent the first one. You've had the first one. If we can prevent the second one, then you're not on that same trajectory for needing potentially both your knees replaced by the time you're 50 years old.

Travis

It sounds like that one, my chiropractor visit was very well timed to this interview. But also, it sounds like that maybe part of what you're trying to do is help people better understand how to have patience, especially at a young age.

Robin

Yes, and to be comfortable having the conversation about some of the fear components to this. Again, remembering that these are 14 to 18 year olds often, they aren't willing to admit necessarily verbally that they feel like everything isn't great because they want to go back to sport. Again, we all understand this. The majority of us that are in this space either are still athletes or you know, air-coated athletes or were. And so understand the desire to be on the field, understand the desire to be active and be out there with your team. The counter to that is, and that's the hard part to explain, is if you push this too fast, you may be back for a few weeks or a few months, and then you'll be back out again for another, you know, nine plus if you tear again. The other thing that we know is that you are at risk for other musculoskeletal injuries after you've your ACL tear. So while we're focused on the second ACL injury, there's also literature out there that speaks to muscle strains and ankle sprains and other lower extremity injuries that happen as people are going back into sport. And so lots of questions on how do we need to modify that process? And so you're just kind of tossing an athlete back in with their team what does the ramp up look like in terms of how they're going back into the sport to prevent some of the other kind of overuse musculoskeletal injuries. So it's a good thing for us in the research base. There's still questions to be asked and answered, but definitely I think the conversations again with the athletes, but then also with their parents about like, what's the realistic timeline that we're talking about and getting them back. And let's think beyond this year to one of the long-term implications of potentially going back too early.

Travis

Well, what general advice, just whether it comes to preventing an initial injury or preventing a re-injury, but what's just some good general advice for maybe an athlete of all ages? I'm asking this specifically for my own self-interest. What can you advise me to do to better take care of myself?

Robin

My favorite topics is don't specialize in sports too young. So that'll always be a thing that I say, especially if we're talking about younger athletes, make sure that people are moving and moving well. Again, we don't spend a lot of time thinking about that with youth sports in general. Yes, it's important to be active and to be moving. We want to have that 100%. But we also want to be teaching proper form and still thinking a little bit more about when you're running drills and doing things like that. I doing them correctly or am I just kind of doing them because the coach told me I needed to you know, go put you know, do X number of taps on the ball or shoot X number of free throws or are you really thinking about the way that you're doing them? So I think that other piece which is not too much for the athlete but most of the coaches is watching the way your athletes are moving and understand that a lot of this isn't something that is natural. Like it's not something, it's not like walking where we kind of all grew up and we learned to walk and we don't think about it. A lot of the movements that we're talking about are things that need to be trained and need to be well understood. So I use gymnasts as a great example, right? Most of us could not stick a landing like a gymnast could. That took training, right? They do it in a very specific way and you don't see them tearing an ACL. They do a lot of other things and they get hurt in lot of other ways but very few of them are ACL tears, right? So are there ways for us to think about how we're training landing or how we're training cutting and to do that within the confines of the sport that they're in. So there are some great injury prevention programs that are out there and if done consistently have shown benefit. The FIFA 11 plus is the one that is probably used the most. So I always suggest when parents are like, well, what can we do as a as a parent group, you can look at something like that, which is publicly available and say, you know, there are aspects of this that we can begin to implement within our sports program. I always say reach out to your local friendly biomechanist and or PT, athletic trainer. They'll also be able to give you some great ideas on that. But in general, think about, and it's hard, right? When you start to think about, you know, kind of what we term as weekend warriors, people that just go out and They don't do anything all week and then they go out and play pickup basketball. That's a different, that's a different model. Cause what I would tell you is for that group, you probably need to be doing something throughout the week. There's a physical activity component that needs to be there so that you know, have the muscle strength and the coordination to be able to do the things you're getting ready to do on the weekends. And we already mentioned getting older is no fun. So just recognize that as you age, some of that has to change.You aren't going to be able to recover as quickly as you age versus when you were 14 or 15 or 16. think anybody who's in that process knows that well. We all know that historian lasts just a little bit longer than you already do.

Travis

That is the truest thing that has ever been said on this podcast.

Robin

Yeah, getting older is not fun, but that's, you know, we're all going to do it.

Travis

Yeah. Yeah. I guess I'm curious. You study these injuries. Do you also watch sports? Do you like sports?

Robin

Yes, I mean, I was a collegiate athlete, very much sports has been a part of my life my entire life. I was not a basketball player. I played soccer in high school, but not through college. So the injuries that I study are not the injuries that I had, which everybody finds fascinating, but it's just not what I did.

Travis

I’m just curious with somebody that when you study this, have you gotten to the point where you can see like when there's a football game on and somebody goes down, you're like, I know exactly what this is. Like immediately.

Robin

Often yes. And I have the pleasure of being married to a physical therapist. So between the two of us usually, and he's also an athletic trainer, so we often are like, ooh, yeah, that was, or, you know, I've had a number of parents who like, I really didn't think they got hurt. And then they'll show me the video and I'm like, yeah, right there, that step, right? That just comes with time and practice. The students in the lab love our fun game we've nestled. Like I can identify people based on the way they walk. So as they're walking down the hallway, even if I don't see them, I can usually tell who it is. Your cadence in the way you walk is very individualized. So looking at and listening to movement becomes part of what, again, they're still learning it, but what we've all done for a very, very long time. So I think that it's the plus and the minus of watching sports for me is like, When I start to watch somebody who's not moving well and you're like, okay, that's, probably going to end up hurt, but you have no way of intervening in that, right? It's an external thing. So sometimes we do our best to kind of shut that part off and just kind of watch the sport for what it is.

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Travis

And thanks to Robin for helping us better understand ACL injuries, prevention, and recovery. If you or someone you know would make for a great curious conversation, email me at traviskw at vt.edu. I'm Travis Williams and this has been Virginia Tech's Curious Conversations.

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