As we continue to learn more and more about arthrogenic muscle inhibition after ACL reconstruction surgery, we can continue to build better rehabilitation programs for our athletes.
In this episode, the team discusses a recent review article on AMI and its impact on postoperative rehabilitation and return to sport decision-making.
To view more episodes, subscribe, and ask your questions, go to mikereinold.com/askmikereinold.
#AskMikeReinold Episode 367: Management of Arthrogenic Muscle Inhibition
Listen and Subscribe to Podcast
You can use the player below to listen to the podcast or subscribe. If you are enjoying the podcast, PLEASE click here to leave us a review in iTunes, it will really mean a lot to us. THANKS!
Show Notes
Transcript
Mike Reinold:
Welcome back, everybody, to the latest episode of the Ask Mike Reinold Show. We are here at Champion PT Performance with another journal article review for you today. I’ve got Kevin Coughlin, Dave Tilley, Lenny Macrina, Dan Pope, Lisa Lowe here. Anthony Videtto is going to lead this one, but we have a recent article from the Journal of Clinical Medicine that’s entitled, “Rethinking the Assessment of Arthrogenic Muscle Inhibition After ACL Reconstruction: Implications for Return-to-Sport Decision-Making,” which is a narrative review.
And again, I think this is a great article that goes over the current concepts of AMI. So, I think it was really worth talking about. I know we talked about it in the clinic. I’ll put a link to this in the show notes so you can check out this article because you really should. I think everybody should read this article. But Anthony, what do we got? What did they find?
Anthony Videtto:
Yeah, so this was a cool review of what we got so far and where we stand on AMI. So, the goal of this paper was to look at the peripheral and central nervous system mechanisms of AMI and link that to how we define return to sport. Most of the research out there on return to sport pretty much only looks at strength symmetry, functional performance, which is great, but they were trying to find: is there a missing link to neuromuscular deficits? So, it is a narrative review, not a formal systematic review. So, the authors went over all the literature out there and gave their insight as to where we are and then maybe where we need to go from here.
So, in terms of their search that they did, they conducted pretty much a lit review on PubMed, Web of Science, Google Scholar from 2000 to 2024. And they looked at terms like AMI, ACL, quad inhibition, return to sport, and all that good stuff. So, they included peer-reviewed articles, they focused on AMI mechanisms, assessment, and rehab following ACL. And then the studies reported neuromuscular biomechanical or functional outcomes, and they pretty much just excluded non-English publications and case reports, and then any conference abstracts without full text availability. So, they looked at all these studies, and then this is like their summary.
So, they reviewed what AMI was, and I think we all have a pretty good understanding of what that is. But just to give a quick recap, it’s essentially just a neuromuscular mechanism that reduces muscle activation in order to protect the joint. And then we can break that down into two different mechanisms. So, one they’re claiming is peripheral and the other which is central. So, when we have peripheral mechanisms, we’re looking at inhibition of alpha motor neurons that specifically innervate the quads, and there’s two main mechanisms that they’re looking at here.
So, when there is an injury or when the ACL is torn, the native mechanoreceptors of the ACL are lost, and that’s crucial because they play a role in the proprioceptive feedback in neuromuscular control. So, that sensory input is lost, and that’s at the peripheral level. And then when we have that trauma, that’s going to lead to a fusion, whether it’s from the injury or from a surgery. So, this is going to further inhibit that alpha mode neuron excitability, and that’s going to limit quad activation further. So, that’s the peripheral mechanisms that we’re looking at there. And then this can lead to a central level inhibition as well, and then this is where we see corticospinal excitability deficits due to that spinal reflex inhibition.
So, that’s going to alter afferent feedback to the brain, and that’s going to further reduce this excitability of motor neurons. This is also going to state that neuroplasticity is going to be impaired as well, and that’s going to affect motor control in the brain. So, not only do we have neuromuscular control deficits in the joint itself, that’s going to impact quad activation, but this is also going to affect all the way up the chain going towards the brain. So, it’s just going to limit how well the brain can activate our muscles here.
And so then they dive into what’s going to get affected here. I think we all know that quad strength is going to be the main thing that gets affected here, but it’s not just how much output the quads are able to produce, but it’s the overall capacity, and then how quickly we can actually activate our quads. So, then they dive into, “How are we going to assess this in the clinic?” And there were a few mechanisms mentioned that I thought might be less relevant to us as rehab professionals, and that was like EMG. I don’t think we’re going to perform EMG studies in the clinic, but that might be something that, further down the road, we could maybe talk about. But it’s also going to affect reflex and corticospinal excitability.
So, if we can use EMG in the future, that might be something that we look at, but right now, I don’t think that’s something that we’re too interested in at the clinic. So, what they say that might be relevant to us is what are we doing in the clinic to see what’s going on here. So, I think the biggest thing was strength testing, and I think we’re doing that on a monthly, six-week basis. So, I think that’s something that we’re hitting. We’re looking at joint effusion, we are looking at sweep tests, are we taking girth measurements, all that to determine how much swelling is inside the joint because that’s obviously going to limit how well we’re able to activate our quads. And then we’re looking at some functional tests too.
So, vertical jump, horizontal jumps. Are they using a knee strategy? Are they using a more hip or ankle strategy? So those might be ways to determine whether or not we feel like we’re using our quads more if we’re using our hips or ankle strategy there. We can also look at our running analysis because that might impact strategies as well. So, then they go on to make some recommendations on how we might approach AMI in the clinic, and they essentially say this is going to be a multifactorial approach. So, in the early stages, got to hammer NMES, cryotherapy, BFR. And then in the mid-stages, we are going to obviously incorporate strength training, but maybe more of a focus on eccentric strength training just to get that neuromuscular control down.
And then in the later stages, maybe incorporating some cognitive tasks, dual task type stuff, where you’re trying to train the brain while you’re doing some other type of task as well. So, that was just a quick summary on what they found and what their thoughts were on where we are in the literature. I can offer my thoughts, but I’d love to hear what everyone else came up with when they were reading this article as well.
Mike Reinold:
Awesome. Great job, Anthony. I thought that was really cool. And I think this is an article everybody should read. So, you should go check it out because it does talk about our current concepts and our understanding of what AMI is and the potential factors, because there’s a lot going on with AMI.
And then what I think is really cool is they try to take that information and they come up with that three-phase approach on how to tackle that, early, mid, and late phase, and different strategies we can do. Because when you build a comprehensive rehab program, hitting all these things is awesome.
So, that’s what I thought was really cool. That was good stuff. So, what do you guys think? What are you guys going to do different for, I’d say, assessment and treatment of AMI based on this? Who wants to jump in on this one? Dan?
Dan Pope:
I think we all agree that it’s a problem. I think, at least for me, and I think just talking to everyone at Champion, I think the trouble is figuring out how to intervene and then some assessment to see when we could potentially pull back. Because I was talking to Videtto, it’s funny because I just tried something the other day with my patients had knee effusion, but we can use some biofeedback, like an
And that would be interesting and one way to measure it. But I think the takeaway from there is like, “All right, we know that inhibition is there. What do we do to address it? Do we do more NMES? Do we do more biofeedback? Do we do ice more?” In some of these studies, where they were looking at NMES being effective for quad inhibition and improving strength, essentially, they had people doing an hour of NMES every single day. It’s not necessarily practical in a clinic. Do we need to send more people home with this unit? What if they had people do an hour of BFR training every single day as opposed to NMES? Would that change things?
If we just had people do another extra hour of isometrics and quad sets, would that be the same as using NMES? So I think that it’s very relevant. It’s good, I think, but we lack good ways to assess it, and I think we lack high quality studies to see what intervention is going to be best. But I think it’s good that we’re at least admitting that it’s a problem and trying to figure out ways to solve it.
Mike Reinold:
I love it. Any time Dan and Kevin especially review an article, they highlight to me the point that every article, it answers one question and asks five others. And that’s a really good point. Of everything Dan just said there, there’s so much that comes out of this. The interesting thing on biofeedback, Dan, that you made me think of when you said that, was I think a lot of times too early in the rehab process, the patient compensates and they just think the goal of the task is to do a step down. And maybe they have more of a hip-driven strategy versus a knee-driven strategy or something like that. There’s a way that they’re compensating because they’re just trying to achieve the task that you gave them to step down.
But if you use EMG, for example, just biofeedback-based EMG that we can do in the clinic, and just have them early on, just say like, “Oh, no, no, make sure you’re contracting that quadricep.” Sometimes just even simple things like that may be an effective thing that we can add to it. Now, if there’s neural inhibition, that may not necessarily work, but to me, I think that’s one of those foundational things that sometimes we skip, is that we allow people to compensate through something for probably a little bit too long sometimes. That’s where biofeedback can really help. I thought that was pretty cool, but what else? Who else had some thoughts on this? What are you going to do different, Kev?
Kevin Coughlin:
Yeah, I guess what I was thinking as I was reading the article and Anthony was going over it was that I wonder what you and Lenny think about this too, because it seems like these concepts have been around for a long time, but now they’re just putting a name to it and you see it more and more in the research, the term AMI. I mean, some of the neural-driven stuff might be a little bit newer as they’re learning more and more about those different pathways, but I think the concept of reducing swelling and trying to achieve a quiet knee is another way of just saying that you’re reducing AMI. So, I wonder if Lenny has any particular thoughts on that and how that’s just evolved a little bit over time.
But then I think what Dan said rings true, and this is where we just have to be on the lookout for more research, because I almost left the article thinking, aside from achieving a quiet knee, what are the other strategies that we can do in the clinic? And I know they had said NMES, but like Dan said, they were recommending doing it for an hour, which isn’t practical in the clinic. And if someone has one of these devices at home, that might be helpful. And I think just other research Dan and I have looked at a little bit about the vibration therapy being helpful and cryotherapy being helpful, but I still think of all of those as strategies to achieve a quiet knee, a less painful, less swollen knee.
So, it seems like if you can do that, you are working on AMI, but I know we’ve all seen in the clinic those persistent cases where it just doesn’t seem like that person has good quad activation, however far out. And it would be nice to see more research coming out that focuses on some of those different mechanisms, whether it’s like mental imagery type stuff or dual tasking, if that stuff starts to help. But yeah, I think a good article and something to put a name to these phenomena we all see in the clinic with the post-op patients.
Mike Reinold:
Before Lenny jumps in too, I would just say sometimes this scares me when we start going down this route a little bit here. So, anytime we see weakness after a surgery, you don’t want to immediately label that AMI. It could just be weakness because if you think the strategy for getting somebody strong is to ice and then doing some dual task balance exercises, you’re going to have a weak person for a very long time. So, I think what this progression has done for us is it shows us, again, you can’t just do one thing.
You can’t do just muscular. You can’t just do neuromuscular. You can’t just do neurocognitive. You have to put them all together. That’s my fear here is that we turn into a bunch of PTs, that there’s lights glowing everywhere, and we’re throwing color things and doing math equations all the time and we’re not getting strong. I think we have to be careful of that. So, that’s just one of my caveats. But maybe I stole Lenny’s old man thunder. Lenny’s even crankier than me, but what do you think, Len?
Lenny Macrina:
My coffee tasted so good this morning. I am not cranky. No, I mean, yes, of course. And it’s funny because I look back in my career, and when we were in Birmingham and stuff we were doing, a lot of it’s the same. It’s just my strengthening has gotten better. I’m a better strength coach now because we have the gym. But dual task stuff, we’ve been doing this stuff for a couple decades.
Mike Reinold:
Yeah, totally. I was explaining that to the students.
Lenny Macrina:
Yeah, we’ve been doing this. I think we knew what we had to do. I think we have maybe a little better understanding of the “why” we were doing it. I think we knew you had to throw something at somebody while they were doing a task that we thought was going to help them get back to their sport. But why, maybe now we know why it has to do with the sensory effects on the brain versus the visual motor cortex being utilized. The brain stuff that Dustin Grooms and Meredith have put out has really helped us, and Grant North. And so I think we’ve had the concept. Now we have a better understanding of the why, and I think that’s key. This paper, Florian is a great author or a great researcher.
Him and I have communicated a bunch over the few years that I’ve gotten to know him as a researcher and he puts good stuff out, stuff that’s very useful for us. So, look at his research on other stuff too, meaning like open chain knee extensions after an ACL. Stuff that he puts out is very useful to apply right away. So, I think this paper is a good overview of what AMI is. Again, I think our limitations as clinicians are that we don’t have access to a lot of this equipment. So, we have to just trust what is being used out there and recognize, when we have a patient in front of us, that it hopefully has been studied with somebody who has an isokinetic dynamometer or some kind of force plate or 3D gait analysis or something like that.
And then we need to somehow apply it to our patients. Meaning we’re doing the stuff that the researchers are telling us to do, but we have to apply it correctly and in the right dosage and stuff like that. I think most people are underdosed when they train people. And so I think having a good strength and conditioning program, like it says, do eccentrics. Well, of course, we do eccentrics. Just, are you dosing it correctly, and are you challenging the person enough over the 9, 12, 15 months that they’re in PT with you? So I think overall, good paper. I had read it previously too when we decided we were going to do this.
So, it was a good re-review for me, but load people, get them doing dual-task stuff, but the basics, patella mobility, get hyperextension of the knee that’s symmetrical to the other side, eventually, not immediately. Eventually get their gait going through external cueing, internal cueing, quad strengthening, basic stuff like that, I think is just all the stuff that we’ve always done. And now we have a reason why via this paper and other people’s research.
Mike Reinold:
You know what, Len? I was just thinking what we need. We should come up with a course that’s non-AMI restoration of strength. Because if you lose patella mobility, your quad strength’s going down. If you lose knee extension and you lose the passive range of motion, your quad strength’s going down.
Lenny Macrina:
Yeah, the basic stuff. I know.
Mike Reinold:
Blah, blah, blah. And it’s not motor imagery. You have a mechanical issue. There’s still mechanical issues that play a part in this.
Lenny Macrina:
Still see a bunch.
Mike Reinold:
Yeah, huge.
Lenny Macrina:
Still see a bunch. I inherit people that are four, six months out. They’ve exhausted their benefits. “Alright, go see Lenny, go see another PT” or whatever. And it’s still a patella mobility issue. It’s still the swelling, which we talked about in a previous podcast. There’s still the basics that they were underdosed, and they were just doing three sets of 10, wall sits, or isometrics, versus “let’s load them appropriately.” So, yeah, it’s still a basic lacking that’s going on.
Mike Reinold:
I like it. Anthony, did we miss anything? Any points that you had that we missed?
Anthony Videtto:
No, I think we hit everything, and I just wanted to reiterate, I think we are doing everything we’re supposed to be doing, but this just highlights and reinforces that what we’re doing is correct. The only other thing I thought maybe we could quickly discuss, if we got a little bit of time, was in terms of swelling, let’s say two plus, three plus swelling, we haven’t gotten to that one plus swelling yet. Is that something that we’re getting into the gym maybe a little bit too early if we’re still seeing that, and is that going to lead to some poor movement patterns because they can’t fire their quads?
So we’re trying to do a squat, and next thing you know, we’re using more of a hip strategy, and that may lead to some deficits down the road. So, is that something where maybe we need to stay on the table a little bit longer, do some more isolated stuff? Love to hear your guys’ thoughts on that, on whether or not two and three plus swelling is more of a criteria base to really get them to one plus before maybe we’re getting them into the gym.
Mike Reinold:
You go, Dave.
Dave Tilley:
Yeah, so I actually have someone who’s literally this right now. So, she’s had an LAT, and Lenny and I have had some discussions back and forth, but she just had some pretty notable quad atrophy, AMI probably after, but she had an LAT and she just was really swollen. Her knee was just, as Lenny said, just looked angry for more than we would expect. And so it was slower to get her off the crutches. It was slower to get her unlocked off the brace comfortably. It was slower to get her back to just feeling hyperextension as close. She has good bending. I don’t know, maybe she was at school still, she had prom, she wanted to go to prom.
So, maybe she was doing a little bit more than we would like her to do in the first eight weeks, but her knee just stayed a bit more swollen and a bit more AMI in the quad than I wanted to. So, normally around… She’s 11 weeks right now… We’d be in the gym doing a pretty formal two-day program around what her graft choice was.
And I just told her straight up, I was like, “Hey, we could start pushing things a bit more, but we have some basics here that are not met. You still come in missing a couple degrees of extension, we have to get it back. It’s still a little more swollen, a little more sore. So, we’re just going to stay on the BFR, STEM train and do some basic stuff and just keep hammering your quads until you feel as though you can walk comfortably without pain, and still we feel like your basics are all met.”
In the long-term, maybe she gets back to sports two months later because then everything went perfectly smooth in the beginning, but maybe she’s two months delayed. What does that matter in the context of – this girl’s trying to get a scholarship to a very high-level university and get a full athletic scholarship. Does two months matter in the long-term of four and a half more years of sports? And in this case, I don’t think it does.
So, I told her just straight up, “It’s going to go slow. This is going to be a boring three-month grind to get your quad strength back up because we were a little delayed, didn’t do anything wrong, but this is the boat we’re in. So, let’s just ride this out by time-based criteria. A little less in performance, objective measures a little more.”
Mike Reinold:
Nice. Good job, Dave. I like it. Anthony, great job on the article. Yeah, I think this is a really important article that people should probably read. Anthony talked about it in the lens of, “What are we going to do different at Champion?” You guys are almost sitting in on our journal club and us talking. And Anthony said, “We’re hitting most of these things.” But if you’re not, or if this is a new concept for you, be sure you read this article and make sure you are incorporating all these things too. I think that’d be really important. So, head to mikereinold.com and subscribe. Make sure you get notifications when we do some more of these, and we’ll keep plugging away. I hope you enjoyed. Have a good one. Take care.
