176. PCL (Posterior Cruciate Ligament): Function, Injury Mechanisms, Assessment, and Rehab Priorities

In this PT Snacks episode, Kasey breaks down the posterior cruciate ligament (PCL) for PTs and students, covering what it is, how it’s injured, and how we assess and manage it clinically. We review the PCL’s role, common mechanisms of injuries, plus what combined injuries may indicate. We also hit key exam findings and tests, imaging options, grading, and broad rehab principles focused on protecting against posterior shear, progressing quad strength, and using protocols thoughtfully while testing readiness stage to stage.

00:00 Welcome to PT Snacks
00:31 Support the Podcast
01:13 What the PCL Does
01:35 Anatomy and Bundles
02:49 Injury Mechanisms
04:08 Symptoms and History
05:09 Clinical Tests and Imaging
06:04 Grading and Treatment Paths
07:18 Rehab Principles and Progression
09:14 Protocol Reasoning and Homework
11:34 Wrap Up and Contact

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Transcript

Hey guys. Welcome to PT Snacks podcast. This is Kasey, your host, and if you're tuning in for the very first time, what you need to know is that this podcast is meant for physical therapists and physical therapist students who are looking to grow your fundamentals in bite-sized segments of time. Now, today we're gonna be covering the PCL or posterior cruciate ligament, and I can't believe that I haven't covered this before, but we're gonna cover it today. So we're gonna cover exactly what it is. How this gets torn and what do we do about it. Before we do that, if you are enjoying this show, it's been helpful to you. You've used it on your clinical rotations. If you wouldn't mind supporting the show in one of three ways, that would mean a lot to me. The first one is just, if you know somebody who you think would benefit from this show, tell 'em about it. The second one is to just leave a review wherever you actually listen to this podcast. Uh, that really just helps. The show to grow. And then the third one, if you feel led to give financially, that just helps to support some of the fees that go into making this podcast actually a thing. 'cause it is a one woman show that's appreciated, but do what you can. Uh, and then, uh, anything is appreciated. Right. So with that being said, let's dive right into what is a posterior cruciate ligament. Okay, so what is the PCL? So essentially the PCL is one of our largest and strongest intraarticular knee ligaments. That helps as a primary posterior stabilizer, so it helps to prevent tibial posterior translation. It's made up of two main functional bundles. We have our anterior lateral or AL bundle, and then we have our posterior medial or PM bundle. The AL bundle or anterior lateral is gonna be larger and more vertical. It's more dominant in mid flexion for posterior tibial restraint, whereas our posterior medial bundle is smaller. A little bit more oblique, more key in extension and deep flexion. So they work together essentially to help stabilize the knee. It works with the anterior posterior meniscus femoral ligaments that form up to four synergistic fiber bundles that help to resist posterior rotary loads. 'cause we like to do some twisting and stuff like that in sports, right? So the function, as I mentioned before. The PCL is a primary restraint in posterior tibial translation, especially at higher flexion angles. It's also a secondary restraint to various and valgus forces and external rotation. Chronic high grade deficiency can increase contact pressures and accelerate medial and patellafemoral degeneration. So something to consider if. Someone has torn this ligament on what are their treatment options moving forward? How does this happen? PCLs can account for 17 to 20% of knee ligament injuries often in young adults. So when I say young adults, I mean 20 to 35 years old. Um, the most common mechanisms will be like a dashboard injury where there's an anterior force to the proximal tibia and the knee is flexed. So like sitting in a car and get hit by a dashboard in a motor vehicle accident, that's the classic Cause there are other ways that you can do this. 'cause not everybody who tears their PCL has a dashboard injury. Um, it could also be sports trauma. Someone could fall on a flexed knee with a plantarflexed ankle, um, collisions and soccer, rugby, football, skiing, things that involve you running into things with your knee. A hyperextension or hyper flexion event can cause proximal tears and anterior tibia plateau compression fractures can also. That do that too. Um, an excessive ves or valgus or rotation often means there's a combined PCL and posterior lateral corner or other capsular ligamentous injury that's involved. So some things to keep in mind. That's why it's important to understand the purpose of the PCL so that you know that if something failed in its purpose, what is the thing that failed that I should screen out for? Now in terms of symptoms, this could be acute. There's gonna be pain, swelling, and hemo. Arthrosis. Their pain can also often be patellafemoral, anterior, medial, or posterior pain, isolated tears. They may feel some instability. Could be subtle feelings of giving away or. More typical and chronic and combined injuries.. Depending on how bad the injury is, sometimes it's a matter of you might get some false positives for a lot of tests. So you're trying to control for the most severe thing and then assess as you go. So, in terms of trying to figure out, does someone in front of you have a PCL injury, their history's gonna be important. Such as did they have some sort of dashboard injury or. Fall or hyper reflect, that happened? Was it a high energy or sport like activity? Um, how long has it been since their injury happened and what are the functional demands that they're trying to get back to doing? Common tests that are used for PTs would be like a posterior drawer test. Um, this is found to be pretty highly. Sensitive and specific for PCL injury. So essentially you're, the posterior jaw is where you're seeing if there's an excessive posterior translation of the tibia on the femur. Um, there's also posterior sag sign and a quadriceps active test pretty similar to the posterior drawer test. And then varus and valgus and dial test to screen for PCL and MCL involvement. MRIs are gonna be pretty much the gold standard for confirming if there's a PCL there or not. And they can also identify if there's concurrent meniscal, chondral or other ligamentous injuries. Um, stress radiographs can help to quantify if there's any posterior tibial translation graded injury. They can predict P-P-L-L-C involvement, as well as just ruling out some other things. So there are different grades of injury that can be applied to the PCL. Grades one through two are gonna be more partial or moderate. There's not as much posterior translation, whereas like a grade three we're talking about a complete rupture with marked posterior translation. Now, depending on where you are in the the country, what country you're in will determine what's the norm standard practice for what happens to these patients on certain. Depending on how severe the injury is but some lower grade injuries, they may be managed non-operatively while patient, when patient demands are pretty low to moderate, meaning they don't need to go out and play rugby and compete. They're not at a competitor level. They just need to maybe stand and do the dishes every once in a while. For surgical considerations, that's gonna be for people who have larger demands. On their activities or things that they wanna get back to doing if they have multi-ligament injuries. Um, high grade laxity. Um, concurrent injuries like meniscal tears, things like. That that they're already going in for, they might just go ahead and do the PCL. And again, depending on where you are in the country and who you work with, generally the theme of progression, whether someone's. Being treated non-operatively or post-op really is in the beginning. You're trying to kind of protect the knee and create a healing environment by reducing excessive demands that. Are too much of a stress on the knee and on the joint for what they are ready for, and then slowly build their way back up to it. So in the beginning, there's more of a protective period where you're trying to avoid things that cause excessive posterior translation. Um, maybe they're. Put in a brace to help manage that. Maybe their weight bearing precautions are adjusted to keep them successful. Maybe they have crutches, et cetera. And then you're trying to help improve their pain for your range of motion to, without a posterior sag, they may progress to more quad focused strengthening. Trying to avoid things again that kind of replicate that posterior jaw in terms of your exercises. You may also throw in, hip strengthening, hamstring strengthening, proprioceptive neuromuscular training, and then eventually working towards more return to sport. But essentially, you know, in the beginning you're trying to protect the graft from a lot of posterior shear, so they might not be doing a lot of early hamstring loading, or high flexion, open chain knee flexion. You're watching for posterior sagging in their range of motion when you're looking at flexion. Um, and the progressive quadriceps, again, depending on what all they've got going on, uh, they might be looking at. Whatever other injuries, if there are concurrent injuries that are going on, you're gonna treat it by the most conservative needs that are there, whether it's the PC or another. Tissue that was disrupted essentially. Again, this episode's not really necessarily about specific treatment. Um, I want you to understand more of why the protocol that you have from a surgeon might be in place because we need to consider more of. What the healing timeline is of the tissue that's aggravated, so it's a ligament and help to protect that tissue until it is ready for more stress to then help it to then adapt and be able to handle more and more stress down the road. If we applied stress to early, we are at risk. Of doing more harm than good. If we don't apply enough stress, we are at risk for not preparing them to get back to the activity that they need to do. So it's really about understanding what the needs of the tissue are or tissues, if there's multiple injuries that are going on, and understanding what its job is so that you can offload it from its job while it's healing, and then ask more of it when it is ready to accept load. We are not going by. Social media standards or what this pro athlete could do, we're going by what the body biologically is ready to do. Okay? So I would challenge you with this to, if you have a protocol or you can find one online, go through that and try and explain to yourself understanding the job of the PCL, why certain things come at different aspects of the protocol, and . And then understanding how are you gonna test to make sure that they're ready for the next place in the protocol. 'cause we don't wanna just blindly follow the protocol. We need to test the patient that is in front of us to make sure that they show that they have gotten the foundations that they need from each stage before they move on to the next one. We want to set up our patients for success. That was longer than I meant to spend on that portion, but I hope that is helpful to you so that what you should have gotten from today is understanding what the PCL is, what its job is, how does it get injured, how do we assess it? And then I would say my homework would for you would be able to take a look at your protocol and understand why are you treating it in that way based on what you know about. The setup, how it was injured, how it was, um, what its job was, et cetera. If you have any questions, feel free to reach out at pt Snacks podcast@gmail.com. You can also find me on YouTube, Instagram, TikTok, probably too many places. Or you can join the newsletter and every week I try. And with every episode I try and send out an update on what the episode's about. You can just reply to me on that one too as well. But other than that, I hope you have a great rest of your day, and until next time, okay.