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Scott Webb: ACL and meniscus injuries are fairly common in young athletes, especially young female athletes. And though these types of injuries can not be prevented per se, a lot of research is being done to understand why these injuries occur and how best to treat them. And I'm joined again today by Dr. Kevin Shea, he's the Director of the Sports Medicine Program at Stanford Children's Health. And I'm also joined again by Dr. Emily Kraus. She's a Pediatric Sports Medicine Specialist at Stanford Children's Health.

This is Health Talks from Stanford Children's Health. I'm Scott Webb. So it's really great to have you both on. Last time, we were talking about female athletes. This time, Dr. Shea, I want to talk about ACLs and meniscus injuries, which I know are very common. And before we get rolling with that though, tell everybody what is an ACL exactly. I think we all think we know, but I want to hear it from an expert. And also what's a meniscus?

Dr. Kevin Shea: Brief little anatomy summary, that there are a number of ligaments that function to stabilize the knee. So when you plant, shift, change direction, you rely on soft tissues to make sure your knee is stable and gives you the support you need to quickly change direction. The ACL is one of the critical ligaments. There are other ligaments as well. But the ACL is one of those critical ligaments for knee function and stability. And unfortunately, it's one of the ligaments that does not heal in the vast majority of cases after tear. So it's very important for knee function and stability in athletes, but also sometimes for routine daily activities.

The meniscus has a little different role, but it does contribute to knee stability as well. But one of its primary roles is to cushion the ends of the thigh bone from the ends of the shinbone. It acts as a shock absorbing and shock and force distribution device. So it lowers the pressure on the joint and is good for the long-term health of the knee in terms of knee function, knee stability, but also preventing arthritis. The ACL and the meniscus, so they are partners, if you will, in terms of knee stability. They both work together to stabilize the knee for optimal sports and activity function.

Scott Webb: Great. I love that we can just kind of rewind a little bit and get a little bit of anatomy 101 in here. And how do ACL and meniscus injuries happen? Sometimes, you know, especially from my experience in watching sports, it seems like they're not contact injuries, that they just sort of happen. In other words, athletes don't know they're about to happen. They don't know they're going to tear their ACLs, but maybe from an expert here, how do these injuries actually occur?

Dr. Kevin Shea: Yeah, and you're right about that. And it's a bit surprising. Some people think that contact is the primary driver of ACL and meniscus injuries, but probably at least 60% to 70%, if not 80% or more of ACL and meniscus injuries are non-contact injuries. They usually occur in the setting in which an athlete is accelerating or pivoting or changing direction quickly/ the leg is planted to pivot and change direction and that results in forces that can tear the ACL and the meniscus. And in many cases at least 50%, 60% of the time, you'll tear an ACL and a meniscus simultaneously. We do occasionally see collisions between athletes, where the foot is maybe locked on the ground with cleat and then someone collides with the knee, and that occasionally leads to ACL and meniscus injury. But the majority of them are actually non-contact as you mentioned.

Scott Webb: Yeah. And it does seem when athletes, for whatever reason, I seem to notice it more with basketball, but it's not just a basketball injury, obviously. But it does seem like when a player suffers an ACL or meniscus injury or tear, they look like they are in immense pain, but maybe what are some of the symptoms? Is it always that, is it always that just incredible pain and athletes clutch their knees and everyone knows, "Oh no. It's ACL or it's meniscus"? Are there some other symptoms as well?

Dr. Kevin Shea: There can be. Although I think what you described is that sudden onset of pain and that the sensation that something's wrong, there was a pop or a shift, you know, that people frequently describe, "I felt something pop or snap or tear inside my knee." And most of the time, people stop playing. They can't continue. It's immediately painful. It will start to swell within minutes to hours. And it's hard to continue. In many cases, they'll get carried off the field or limp off the field.

There are some exceptions though. I have seen a number of athletes who actually did have kind of what they thought was a bit of a minor sprain or event and continued to play. But it was only later that they recognized they had an ACL injury. But the predominance of cases are going to be a serious pop, shift and they're done and someone's got to carry them off the field and they limped off the field and they're not going to continue.

Scott Webb: Yes. So in terms of diagnosis, obviously, you know, as an athlete might describe to you, I heard this pop and that's probably the telltale sign, right? You just know that if they heard a pop and they had to be carried off the field, it's probably not something minor. It's probably ACL or something like that. But how do you diagnose ACL and meniscus injuries?

Dr. Kevin Shea: We first start with a history. The patients are pretty good historians most of the time, although sometimes it's happened so quickly, they don't recall all the details, but most of them recall some type of a sudden onset of pain or discomfort in which they couldn't keep playing. So part of the diagnosis is the story. We also may ask them about swelling. Typically, with these injuries, you do have some swelling, ACL tears tend to bleed a little bit more inside the joint. And so the swelling tends to be a quicker onset. So with minutes to hours, you'll have swelling, certainly within a day or so. Where sometimes if they just have a meniscus injury, the swelling may not come on as quickly or maybe relatively mild. So swelling is a factor as well.

We also rely on the clinical exam, sometimes right after their injury or in the clinic or emergency room. The exam can help make these diagnosis by detecting differences in knee stability. There are certain exam maneuvers we do to assess for ligament injury.

And then the last thing we think about is imaging. Occasionally, we use x-rays, which show the bone anatomy very well. But the MRI actually shows the cartilage and soft tissue and ligament anatomy much better than that. So it's a combination of history, the examination and then advanced imaging where appropriate.

Scott Webb: Yeah, And you mentioned earlier that these types of injuries don't typically heal themselves. So that being the case, is it always surgery? What are the treatment options for ACL and meniscus injuries?

Dr. Kevin Shea: This is a question we get a lot from patients and families. And non-operative treatment for an isolated ACL injury can work in select patients. In fact, we do have some patients who may not be particularly high demand either by work, sport or recreation. And there is some evidence that especially people who aren't as demanding with their knees can do reasonably well with a rehab program and time. And then they have to be careful with their knee in the future because their knee is perhaps not as stable as it is in the past. And so keeping that in mind, some patients will do okay.

Most of the patients that Dr. Kraus and I see in our clinic setting are usually high level athletes. They're playing soccer, basketball, football, wrestling, lacrosse, sports that require a lot of activity shifting, acceleration and directional change. And most of those athletes won't do well without an ACL. And so that's the concern in the highly active person, regardless of age, a 60-year-old aggressive mountain bike trail runner, skier, maybe just at risk as a 15-year-old female soccer or basketball player. So I think it's really activity as much as anything else, but age probably has an impact.

The one thing that we have learned about young athletes is that if you have a serious knee injury. And let's say you're fortunate, and that you just tear your ACL and you don't tear the meniscus or tear the bone cartilage or the articular cartilage, if you then go back to your high level sport, you're more likely to do additional damage to your knee. So what starts out as an ACL tear that doesn't have any cartilage or meniscus damage will advance with the next injury in which the ACL's torn so your knee is less stable. And now you may develop a serious meniscus or cartilage injury, which may or may not be repairable. So that's the caution and the concern in young active athletic people is that they have an ACL tear, isolated, and then go back to sport. They can go from an isolated more simple ACL tear problem to a more complex ACL combined with a meniscus cartilage problem, which may have a worse outcome in terms of long-term health of the knee and long-term knee function.

Scott Webb: So a followup question, doctor, about the surgically repaired knees, ACLs, meniscus, is what level of confidence can athletes have in those knees? Are they more or less likely to injure the same knee or would it be the other knee? I guess what I'm asking is I'm sure there's a mental component to this about the confidence in those surgically repaired knees and also the physical part. Are they more likely to injure that same knee again?

Dr. Kevin Shea: A couple of questions, and I'll maybe try and take those questions bit by bit. One you asked a question about, are they more likely to re-injure that knee if they go back to their sport? If they go back to a lower risk sports, so you switched from soccer to cross-country or track, you're probably less likely to reinjure the knee. But assuming many athletes go back to the same sport, there's actually a fair amount of data now looking at what's the likelihood of reinjuring that knee or the other knee. The studies are a little bit equivocal. They don't all come to the same conclusions, but there does appear to be perhaps a slightly higher risk of actually injuring the other knee in several studies.

So if you tore your left knee first time and then you go back two years later, and you reinjure a knee, you may be slightly more likely to reinjure the opposite knee ACL. But both of the ligaments are at risk if you go back to high risk sports. And the re-injure rate varies a little bit from the study. It also varies how long you follow the athletes. If you follow the athletes for two years after the reconstruction versus three years or five years, those numbers will change. But I think it's reasonable to say that the risk of reinjuring either the injured knee or injuring the other knee is probably somewhere between about 15 to maybe 30% plus or minus over a three to five-year period if you go back to high risk sport. So hopefully, that addresses that one question.

The other question I think was about getting athletes back to sport maybe in terms of their confidence and do they trust their knees when they get back? And I think that's a critical part. And I tell patients and families all the time, and I know Dr. Kraus and I are really unified in this, is that there's this therapeutic alliance between the patient and family, the physician and the physical therapy team and the athletic trainer team, because all of those groups have to work together to get the athlete back. I can do a very good technical surgical reconstruction, but without a really good therapy team, buy-in from the trainers, the athletic trainers, the physical therapists, the patients, the families, and even the coaches, I don't think we can get as good a result and in particular, getting people confident. You probably need hundreds of hours of exercise to rehab the muscles and the joints and have them ready to go. But you may also need some work with a sports psychologist from time to prepare to go back.

I mean, there's a lot of factors getting our athletes ready to sport or what we call return to sport clearance. And there's many factors. It's partly time-driven, but it's also probably exercise, strength, balance, coordination-driven, and you have to make investments in all of those areas to really be ready to go back to sports.

Scott Webb: Yeah, you definitely do. And Dr. Kraus, I want to bring you in here. Are the differences in injury rates in male and female athletes when it comes to ACLs and meniscus?

Dr. Emily Kraus: There are some sex-related differences that we see both in the high school and collegiate population with females just being more at risk for sustaining an ACL injury than male athletes. And I think it's important to kind of tap into what are those risk factors? And there is a biomechanical piece as far as kind of a movement-related risk factor. So how is that athlete landing? And we're seeing that the landing mechanics of female athletes compared to male athletes are different and put that knee at kind of a more vulnerable angle and position for sustaining an ACL injury.

And interestingly, Dr. Shea and I are both involved in some exciting research with our motion analysis and sports performance lab, really looking at some of these risk factors and studying these athletes, kind of moving forward, kind of getting a baseline of this movement and how this female and male athletes move. And then seeing which of those athletes sustain injuries and which do not, and is there a biomechanical relationship with that? So that's one piece. And then, also just the hormonal risk factor of female athletes and how that changes with the menstrual cycle. There is some research coming out that does look at varying levels of changes in the laxity and how, I guess, stretchy the ligament is during those different phases of the menstrual cycle and how that may potentially put an athlete at greater risk during different stages.

Dr. Shea, do you have anything else to add? I'd love to get your perspective on that as well.

Dr. Kevin Shea: Dr, Kraus, great summary of some of the issues that are really important. And I think some of the key research questions we're trying to address in our motion analysis sports performance lab, some of the data, if you look at injury rates, male and female injury rates at younger ages are fairly comparable in terms of total number. Males probably have a little more in many sports, but if you look at injury rates based on exposure, women unfortunately seem to have higher rates of injury.

So you could take a hundred female soccer players, compare them to a hundred male soccer players, you follow them over, you know, two or three years, the injury rate for the females will be higher. Some sports, it might be two to three times higher. Some sports, maybe three to four times higher in terms of exposure. So women clearly have unfortunately in some sports and probably soccer, basketball, and European team handball are some of the highest risk sports for these young females athletes.

Scott Webb: Yeah. And I've heard that before, speaking to Dr. Kraus' point about the way female athletes land. And after I heard that the first time, I started paying attention to, you know, males and females playing the same sports, but do they sort of look the same while they're playing those sports and how men and women take off and how they land, especially in basketball and soccer. It's really interesting, Dr. Kraus, that even though, you know, men and women have all the same parts, and they're playing the same sports, they often sort of play them differently, right?

Dr. Emily Kraus: Yeah, once you see it, you can't unsee it, that certain athletes and how they land, it just makes you nervous, whether that's a single leg landing or double leg. And, as Dr. Shea had mentioned earlier, as far as the mechanism and the why, these are often non-contact injuries. And so really watching that knee and how that knee maybe what we say kind of collapses inward to some degree or some level, is putting that athlete, especially the female athlete at greater risks kind of based on those mechanics. And so a big question is how do you prevent that? How do you address those risk factors? is there a more of a group training program that we should be working on? There are some already out there that have shown effectiveness. Or is there more of an individual based training plan that should focus on? That certain athletes may need to work more on glute and hamstring strength. Some athletes may need to work more on agility and balance and other pieces, and really activating the right muscles at the right time. So those are questions that we hope to explore within our lab and within some of our future research projects.

Dr. Kevin Shea: I think in terms of trying to explain this to families and patients and coaches, as you know, there's things we can't modify. We can't modify the normal hormonal changes as part of the menstrual cycle. We can't really modify the anatomy of the female knee, which is different than the male knee to some degree and in some domains, but we probably can modify the way people strengthen their legs. You know, men tend to have more powerful hamstrings than women. A lot of women's soccer players have really well-developed quadriceps, but their hamstrings are not at the same level of development. And so we can modify that with training programs to clearly strengthen hamstrings and address some of these muscle imbalances. But we might also be able to change the way people jump, shift and change directions to adopt patterns that are probably less risky and more supportive of long-term knee stability.

And so there is some evidence that injury prevention programs, both in male and female athletes, but even perhaps more beneficial in female athletes because of their higher risk of injury. There's some pretty good data now showing that you can reduce these risks and probably soccer and basketball in particular soccer, because it's the world's most popular sport in terms of participation. The soccer programs in particular are probably the ones that are most likely to reduce these injury rates. So those are those modifiable trainable things that we can address.

Scott Webb: And, Dr. Shea, as we wrap up here, I know you've done years of research on the anatomy of the knee, which we're focusing on today with a focus on pediatric and adolescent patients with open growth plates. So I understand open growth plates require different surgical approaches than those used for adults to prevent growth plate injury. Tell us more about your research in this area.

Dr. Kevin Shea: Twenty, thirty years ago, we counseled people of ACL tears and open growth plates not to have surgery because the risk to the growth plates was too high. And there was some evidence that ACL surgeries performed in adults would damage growth plates and make the leg short or grow crooked, or create deformity issues for kids.

But over the last 20, 25 years, there's been a growing recognition that if you don't treat these knees, the kids will end up doing more damage to their knee and the psychological impact of not being able to play sports is really significant. So the whole orthopedic pediatric sports medicine world has focused a lot of energy on that.

We've learned by looking at the anatomy there are techniques that you can use that are much more what I call respectful of the growth plate. In many cases, they avoid the growth plate altogether or, if they do have to operate near the growth plate, they do it with surgical techniques or with graft choices, the ligament material we use to reconstruct a torn ACL. You do it in a way that respects the physis and minimize the risk of causing some type of a growth disturbance. We've done this early on with three-dimensional modeling and even almost 20 years ago before there was a lot of really high-quality modeling tools available. We did a lot of work with some manual tools that are now automated and readily available for many people.

We've also had access to a very unusual set of tissue sources where we've actually been able to study through cadaveric dissection and anatomy sessions in surgical simulation sections on pediatric cadaveric knee tissue. So we've been able to back up and confirm that many of these surgical interventions do in fact respect the growth plate, do in fact not put kids at risk for developing disturbance after ACL reconstructions.

At a certain stage, the kids are old enough where you can use an adult type of procedure or more of an adult type procedure. But even in that 15, 16 and occassionally 17 year old, you still have to use certain techniques that won't cause a growth disturbance in the future. And that comes down once again to both the graft material that you use, the fixation devices that you use and the surgical techniques as well.

Scott Webb: Well, this has been really educational as a dad with a daughter who plays sports. This is right up my alley. I'm so glad that I got to host these. Just want to thank you both again for your time and you both stay well.

Dr. Kevin Shea: Wonderful. I enjoyed the talk.

Dr. Emily Kraus: Thanks for having us. This was fun.

Scott Webb: Call (844) 416-7846 to make an appointment or go to stanfordchildrens.org for more information. And if you found this podcast to be helpful, please be sure to tell a friend and subscribe, rate, and review this podcast and check out the entire podcast library for additional topics of interest.

This is Health Talks from Stanford Children's Health. I'm Scott Webb. Stay well, and we'll talk again next time.