Joey Wahler (Host): The anterior cruciate ligament is crucial to knee function, so we're discussing treatment options for ACL injuries. Our guest, Dr. Michael Foster. He's an Orthopedic Surgeon at the Orthopedic Center, an affiliate of University of Maryland Shore Regional Health and part of the UM Joint Network. Welcome to the Live Greater podcast series, information for a healthier you from the University of Maryland Medical System.

Thanks for listening. I'm Joey Wahler. Hi there, Dr. Foster. Thanks for joining us.

Michael Foster, MD: Hey Joey, how's it going?

Host: Good. Yourself?

Michael Foster, MD: I'm doing well. Thanks for having me on.

Host: Sure. Thanks for hopping aboard. So first we hear the term a lot, especially those of us that follow sports, pro and college, ACL, ACL injuries. What exactly is the ACL in a nutshell and why is it so important to knee function?

Michael Foster, MD: So you already stated it. I mean, the ACL stands for anterior cruciate ligament, and so it's one of the four major ligaments in our knee, and it runs from the shinbone up to the femur, and it's one of the more important ones for stability of the knee. More specifically, it prevents the shinbone from shifting forward, and it gives us some rotational control as well, which is why it's so important to the function of our pivoting sport athletes, you know, they're doing a lot of cutting back and forth.

Host: So what are the common causes of ACL injuries? And are there any specific risk factors people should be aware of?

Michael Foster, MD: The most common way to tear your ACL is a non-contact injury. So that's where we see it happen most often. Our athletes, when they're kind of doing a cutting maneuver where their leg goes into a little bit of what we call external rotation or bends inwards in a knock knee position, that's the most common way, but you certainly can tear it multiple different ways.

You can certainly get a contact injury from the outside of your knee that can tear your ACL. Sometimes we see it in a hyperextension type injury, where your knee bends backwards almost, but that's more commonly associated with more than just an ACL injury, but there's many different ways to do it. There's a ton of risk factors for it. The ACL has been one of the most studied ligaments in the literature for sports. And so some of those risk factors are modifiable. Some are non-modifiable. The non-modifiable one, patients probably don't care quite as much about it cause there's nothing we can do about it, right?

So being a female, you're at three to five times higher risk of tearing your ACL. Having a smaller ACL. Your ACL lives in a notch in the middle of a knee. Having a smaller notch, being hyper lax, those are all things that we can't really change. It's just the way we were born, it's the genetics that we have.

But there are modifiable risk factors and so the modifiable ones are kind of our landing mechanics. People are at higher risk of tearing their ACL if they land with their knees in that knock kneed position, if they don't land with their knees flexed and they land more in an extended alignment. Also, if you have weaker hamstrings, so like I said, the ACL prevents your shinbone from shifting forward.

So our quad dominant athletes, our quad muscle pulls the shinbone forward. So the people who have stronger quads than hamstrings are at higher risk. Those are the things that you can modify, to lower your risk of having an ACL injury.

Host: Interesting that you mention weak hamstrings. I've been known to have just that. I'm trying to work on it as we speak. And I know from experience that that can lead to a variety of problems. Can't it?

Michael Foster, MD: Correct. Yeah. I mean, you want to be in balance, right? You don't want to be in excess, any one direction throughout your whole body. And so when you have a weakness in one area, it's important to try to strengthen it, to catch up with other areas so you can avoid many different kinds of injuries. Not just the ACL.

Host: Absolutely. So I would think that most of the time when someone injures, tears, especially an ACL, that they kind of have an idea of what's happened right away, but let's say it's not quite that evident. What are some typical ACL injury symptoms?

Michael Foster, MD: I feel like athletes don't always know that they tore their ACL per se, but they know something's wrong. So, typically, if you tear your ACL, you often feel a pop in the knee, and so something will feel like it gave way. And even in some of these slow mo videos you see on YouTube and all, you can see the pop in the person's knee or the shifting.

After you have the pop, most people will have lateral base pain, or the outside part of their knee will hurt after tearing your ACL, and that's because of the way the knee shifts during the mechanism of the injury, you get some bone bruises and they typically occur on the outside part of the knee. The other thing is swelling. And so if it's an isolated ACL injury, the classic textbook swelling is about 12 hours after the injury.

It doesn't happen right away. It's more like the night after the injury or the following morning, people will notice their knee swelled up some. People can get swelling right away, but oftentimes if they get swelling immediately after the injury, there probably was a concomitant or another injury at the time of the ACL injury. But those are kind of the classic historical things that we're asking when we examine these people to get an idea what's going on.

Host: So as you point out, if someone knows something happened, but they're not sure quite what, like if it is an ACL, what are the diagnostic methods you and yours use to confirm that?

Michael Foster, MD: The first thing is the history. We always start with the history and physical exam, right? So asking them the questions that I just talked about, like, what did you feel when you hurt your knee? How long did it take to swell up after? Where was your pain? That gets us a clue initially.

Then we get our hands on the patient. You have to always examine the patient, right? And so the two best diagnostic tools we have on physical exam to diagnose an ACL tear is a Lachman test, which is where we essentially have the patient's knee slightly bent, and then we pull the shinbone forward. If we can see there's increased laxity there, that gives us a big clue that they tore their ACL.

There's also this pivot shift test, which is kind of rotational move we do on exam, and we feel instability with that exam maneuver as well. That also clues us in that there's potentially an ACL injury. That examination maneuver is a little bit harder to do acutely because patients often are guarding or protecting their knee. They have a little bit of pain in the knee, and so they may protect you from being able to get a good feel for that examination maneuver. But if you can get a feel for it, it's pretty classic for knowing they have an ACL injury. After that, then we go into x-rays imaging. X-rays, we always want those because they can show us that there's true swelling in the knee, which we call an effusion.

And if there's any fractures, there's one kind of fracture called a Segond fracture, which is pathognomonic for an ACL tear. We see a little fleck of bone on the outside part of the shin bone. We know you tore your ACL. Most patients don't have that, so then we get an MRI and the MRI is how we get the definitive diagnosis of the ACL tear and then make sure there's nothing else going on in the knee at the same time.

Host: So, treatment wise, first, an exciting study in the British Journal of Sports Medicine found that 53 percent of participants who suffered an ACL rupture and were managed with rehabilitation alone, displayed MRI evidence of ACL healing. So is this consistent with what you've seen in your practice and what kinds of rehabilitation do you usually recommend?

Michael Foster, MD: I would say this isn't totally consistent with what I see in my practice and all the literature that's out there, but that's probably because a lot of our patients, I wouldn't say 53 percent, we're managing non-operatively with ACL tears. This study, you got to look at it critically. I mean, it's pretty awesome what they've done and shown that the ACL can look on MRI two to five years down the road, like it can heal. But from other ligaments in the knee, we know that MRI evidence of the ligament looking intact doesn't necessarily mean it's functioning well.

When an ACL or these other ligaments tear, they get very disorganized, and so even though they may scar in with time and they may look normal on imaging; they still may be stretched out. The ligaments don't stretch out like rubber bands. They stretch out like taffy, meaning they stay kind of loose. And that's where the physical exam findings come into play for us to be able to tell whether the ligament's actually functioning well or not.

In saying that, in our practice, there's a lot of patients we manage non-operatively with ACL injuries. People who don't do a lot of cutting and pivoting sports. People who already have arthritis in the knee. Those are people that we don't recommend reconstructing their ACL because you don't need it. You need your ACL when you're going to be doing those cutting and pivoting sports.

And when we do rehabilitation for these people that aren't getting surgery, we focus, like I talked about before, on strengthening their hamstrings, to strengthen the dynamic stabilizers about the knee, the muscles about the knee, the core muscles, things that can compensate for having a little bit of ligamentous or laxity in your static stabilizers of the knee.

Host: So besides rehabilitation, what non-surgical alternatives are there for those who prefer not to undergo surgery, maybe for one of the reasons you just mentioned?

Michael Foster, MD: So bracing is something that's out there. There's ACL braces that will help prevent the shinbone from shifting forward. The evidence for those braces is conflicting. There has been shown to be help with wearing an ACL brace when you're skiing or doing specific activities, and those can help stabilize the knees, in those people who don't want to undergo an ACL type surgery, but still want to have some level of activity doing things like skiing or cutting sports. Outside of bracing and physical therapy aspect of things, there's not a whole lot that we have to offer for people in the short term after an ACL injury.

Host: So that brings us to surgical options, if needed. What is a typical surgical process for ACL reconstruction? And what's usually the expected recovery timeline?

Michael Foster, MD: Yeah, so that's a, a very, very, nuanced question. There's a lot of information that goes into that, but essentially when you're doing surgery on the ACL, the gold standard is an ACL reconstruction. Okay? Back in the day, a long time ago, they were stitching ACLs back together and they failed at a very high rate.

And so that's where we turned to reconstructing the ACL, meaning, building a new one. When you build a new ACL, you can use patient's own tissue, or you can use donor tissue, and that's based on age and activity level. If you're doing ACL repairs, it's now coming back where people are starting to do those again.

Up in Harvard, they're doing studies looking at what's called the BEAR procedure, Bridge Enhanced ACL Repairs, where they're using a matrix to repair the ACL, and there is some evidence showing that it's as good as a reconstruction, but it's very new, so not everyone's on board with that yet. Typically though, if you undergo an ACL reconstruction, there's a fast rehabilitation protocol and then the more traditional.

The traditional protocol is where people are getting back to all their activities they want to do in sport in nine to twelve months. And that's what most people are following. The accelerated protocol, which we see in some professional athletes who have a lot on the line, a lot of money to get back to play, is around six months.

But in reality, time's the worst predictor. Really it's based on a partnership with you, the patient, and the physical therapist working with them to be hitting metrics, to see how strong their knee is, to see how confident they are in their knee, to determine readiness when to get back to sport.

Host: A couple of other things then. What steps, if any, can people take to prevent ACL injuries? Are there exercises or practices that can help with injury prevention? For instance, you mentioned a couple of times now, weak hamstrings.

Michael Foster, MD: Yeah, that's exactly right. And so there is some prehab that people can do before their sports season that we're starting to implement in our high school teams and things like that, where you actually do jump training, plyometric training, making sure you're landing with your knee and hips flexed, that you're not having your knees kind of turn inward when you're landing in the knock kneed alignment, the position that's at higher risk of tearing your ACL.

So doing that stuff pre-season can help prevent ACL tears. We know that people who have fatigue resistance or people who are in good shape when they go back to do sports. Say someone who hasn't been doing any exercise and then wants to go play pickup basketball on a whim, they're at higher risk of tearing their ACL.

So making sure that we're working hard and getting in shape before we go do these kinds of activities, important to prevent injuries, and then, like you said, working on our core strengthening, our hamstring strengthening, making sure we're staying balanced will give us less risk of tearing our ACL when we do the activities we enjoy.

Host: So good overall balance, loose hamstrings, if you will, and bend those knees and bend them forward, not facing inward.

Michael Foster, MD: That's pretty much strong hamstrings. Loose is good too, but you got to be strong. And so we're, it's mostly strengthening.

Host: better put by you. That's why you're the doctor. Well, folks, we trust you're now more familiar with treatment of ACL injuries. Dr. Michael Foster, thanks so much again.

Michael Foster, MD: Thanks for having me.

Host: Absolutely. And you can find more shows just like this one at umms.org/podcast. That's umms.org/podcast, as well as on their YouTube channel. If you found this podcast helpful, please do share it on your social media. I'm Joey Wahler, and thanks again for listening to Live Greater, a health and wellness podcast brought to you by the University of Maryland Medical System. We look forward to you joining us again.