one of our dissections that you could consider a fan favorite among many of our students is this real human knee And this is for a couple of reasons One it's just incredibly cool to see what a real human knee actually looks like inside And two many people have experienced knee pain due to chronic conditions such as arthritis like this knee actually has but also from injuries such as mild sprains all the way up to a full-blown tear of say an ACL So today we're going to show you a real ACL talk about what this critical ligament does how it's injured and torn and of course discuss the treatment options such as the many different surgical graphs from using a piece of someone's own hamstring to using cadaavver ligaments Plus we'll discuss some things that you can do to reduce your risk of getting a torn ACL So let's get knee deep into this anatomical awesomeness So let's start by orienting you to this real human knee And I'll mention some other common ligaments that you've likely heard about with the knee like the MCL and the LCL but then we'll go deep into that ACL So here we have a right human knee And the reason we know it's a right knee is we have the patella here or the kneecap We know that has to be anterior on the or on the front side of the knee If I rotate this around you can see the posterior aspect or the back of the knee Then we have the femur the bone of the thigh Okay we know that has to be upward Then we have the tibia which is what most people refer to as your shin bone But the tibia is the medial or the inside bone of the lower leg And then we have the fibula right here which is the lateral bone of the lower leg And because of that we know this has to be a right knee Now I'm sometimes a little obnoxious with my students Sometimes they'll say tibia and fibia and I'm like no no it's tibia and fibu la Because the la reminds you it's the lateral bone So again if I tried to orient this to myself because that fibula has to be on the outside we know it's a right knee If I tried to put it on my left side that fibula would be in the incorrect position there So let's take a look at some of the cool ligaments on this knee Here we have the MCL or the medial collateral ligament because it's on the medial aspect of the knee that thick band there If I rotate it to the outside you can see the LCL or the lateral collateral ligament here Now these are considered extra articular ligaments because they're on the outside of the joint capsule But if I reflect the patella out of the way we can see the inside of the knee And we'll go into those two ligaments in just a second But as an added bonus I just wanted to mention that this is a pretty unhealthy knee from a cartilage standpoint This has pretty much moderate to severe arthritis All of this cartilage is pretty much worn out to varying degrees But if you listen closely got a little bit of cartilage left right there But listen to this Pretty much all the way down to bone Now we have a whole video on arthritis where we go into more detail of that So if you want to take a look at that I'll link it at the end But let's take a look at the ACL and the PCL And before I point those two ligaments out that you can see right in between those two condiles of the femur there The ACL stands for the anterior crucet ligament and the PCL stands for the posterior crucet ligament Crucet referring to crucifix because these ligaments are going to form across with each other And if I kind of just orient you at least show you the direction that they run The PCL is going to run in this direction where the ACL is going to run in that direction And we can only see a little piece of the PCL from this view or this cadaavver dissection that we have here And I'm just going to touch it with the probe And just right there the tip of my probe is the PCL going backwards And I'll remove the probe out of the way So just that mass of tissue right there that's going to move backwards But the ACL we've got a pretty good view here I'm pinching that whole ACL right there in the probe But let me just get you a cooler view of the ACL with the tip of the probe there You can see it running backward like so Now I'm going to show you another cool need to section with that has the ACL And I'm going to twist it and put some different tensions on it to show you what the ACL is supposed to do and how you can potentially tear it So that'll be fun in just a second But I do want to just talk about ligaments in general what they do and how you pretty much can tear them So often in anatomy you'll hear like tendons connect muscle to bone whereas ligaments connect bone to bone and that is true That is part of the definition of a ligament But we could do a little bit better with the definition of ligaments because ligaments connect bone to bone they are going to stabilize the joint but they also will define the range of motion of a joint So what do I mean by define the range of motion so if we come back to the knee here we learned like the MCL the LCL and the ACL and the PCL Those ligaments are essentially saying to the knee you can move in this direction in this direction and a little bit of rotation If your knee's bent if you were to say have your knee go in this direction or have a force put a valgus strain on your knee your MCL is going to be pissed If you got your lower leg forced in this direction your LCL is going to be really mad Let's say you got in a car accident you weren't wearing a seat belt and your tibia hit the dash and shoved your tibia backwards your PCL is going to be pretty upset about that as well And so what you're seeing is that the ligaments define the range of motion of a joint and they provide this tensile resistance kind of like a rope but with enough force you can snap a rope or in other words you could snap a ligament Again if you pushed the leg in one direction too far and so what about the ACL what is the ACL resist and again how can you tear it well we're going to answer that on this other cool cadaavver dissection But before we get into this other cool view of an ACL on the other cadaavver dissection and because it's totally normal to talk about food while in an anatomy lab I've got to tell you about something that's made my life a lot easier And that is the sponsor of today's video Thrive Market If you haven't heard of Thrive Market it's this awesome membership-based online grocery store where you can get highquality healthy products shipped right to your door at memberonly prices That means less time wandering around grocery aisles and more time doing whatever it is you do when you're not watching your favorite Institute of Human Anatomy videos But you could eat food from Thrive Market while watching those Institute of Human Anatomy videos Now I have at times been known to be a picky eater Most of the time I want clean labels with no weird additives and definitely minimal amounts of junk Thrive Market bans over 1,000 what you could consider sketchy ingredients We're talking no artificial flavors sweeteners colors all those extra ingredients you don't want Plus I've been loving their low sugar high protein snacks And you can filter everything by dietary needs You want keto vegan gluten-free high protein it's all in there You can even hit buy again and restock in seconds which is great for people like me who routinely forget their lunch So if you're ready to upgrade your grocery game click the link in my description box or go to thrivearket.com/human anatomy to receive 30% off your first order and a free gift when you join Thrive Market today And now let's get back to ACL tears So here we're zoomed in to a different right knee Here's the bottom or inferior portion of the femur Here's the top of the tibia And here again we have that awesome ACL that I'm pinching with the probe I'll move the probe out of the way there so you can see it a little bit more clearly But again there's that ACL going up into the knee Now the reason why we move to a different knee dissection is that due to the nature of this dissection I have a bit more wiggle room quite literally so I can put varying degrees of tension on this ACL so that I can show you its functions and potentially how it can be torn Now one of the main jobs of the ACL is to prevent anterior translation of the tibia So in other words it's preventing or stopping the tibia from sliding too far forward And if I come up to this dissection watch what happens when I pull the tibia forward You can see that ACL gets tighter and stops that anterior translation of the tibia And this is very similar to a test that many clinicians in like a sports medicine clinic or an orthopedic clinic may perform on a patient if they suspect an ACL to be torn It's called the anterior drawer test They have a patient lay down They'll have them bend their knee in a very similar position that this cadaavver knee is in and they'll come up to the tibia push it back to put a little bit of slack on that ACL and then quickly pull forward And if the ACL is intact like this particular ACL you'll see it has that nice solid end point and it stops the tibia from going any further forward If they don't have that nice solid end point that would indicate to the clinician that this person could very well have a torn ACL Now something else that the ACL prevents is internal rotation of the lower leg So twisting it inwardly And if we come over here and do that same thing to this leg you can see as I internally rotate more and more that puts more and more tension on that ACL and that ACL is going to try to prevent that Now the ACL will also limit hyperextension So if I straighten the knee fully if I were to continue to go forward that ACL is going to try to stop and limit that So in other words how an ACL is torn is the knee is pushed in one or a combination of those directions In other words it's pushed too far in one or more of those directions And this could be done through like say like a contact injury injury like in American football If somebody got hit on the lower leg and pushed the knee too far in one of those directions it could tear the ACL What's interesting though is that 70% of ACL tears are actually from non-cont injuries So somebody may land from a vertical jump in a funny position or they may plant and twist and that ACL could pop Now there are again varying degrees of injuries or how bad the ACL can be torn You could have micro tears in those collagen fibers that build up the tendon and in those cases most people may opt for like physical therapy rather than a surgical procedure But if you fully tear the ACL and you want to continue in sports and have a high level of physical activity then you're more likely going to want to opt for surgery And there are multiple different surgical options Maybe you've heard of people saying "Oh they used a my hamstring to build me a new ACL or a patellar tendon graft." Or maybe you've heard of cadaavver uh grafts or alligraphs that they use to actually replace somebody's ACL So we're going to actually take a look at some of those options on the next cadaavver dissection So as I just implied with ACL surgery or ACL reconstruction we're going to need some sort of graft or tissue from the person's own body or tissue donated from another body And that's where you'll hear about cadaavver ACLs and we'll get into that in just a second But if the tissue comes from the person's own body it's referred to as an autograph because auto just means self And the two most common sites where you'll get this ACL autograph are either from the hamstrings or the patellar tendon Well let's start with the hamstrings The hamstrings are actually made up of three individual muscles We have the biceps feorous By means two seps means head So we have the long head here and then the short head underneath We also have the semimebrosis and you can see how awesome that membranous tendon is and hence why it got called the semimebrosis And the third muscle that makes up the hamstring is the semi- tendinosis And you can see how long this tendon is and why it got the name semiendinosis But this is the tendon that can be used to reconstruct an ACL Now you technically could potentially use the graasilus tendon as well but that's not a hamstring But coming back to the semi-eninosis tendon this tendon is so long that the surgeon can take that tendon fold it back on itself multiple times stitch it together and make this incredibly strong ACL stronger than the original actual ACL But there's always pros and cons to each one of these procedures One of the pros is how strong this new constructed ACL can be But when the surgeon takes this graft it doesn't come with any bone blocks or bone plugs And so in this case the fixation to the tibia and the femur needs to be done properly with screws or other fixation devices Whereas if we come over to the patellar tendon option they would take a portion of this patellar tendon to build a new ACL and they'll actually take a piece of the patella so piece of bone there and even a piece of the tibia So with this particular graft you're going to have two little bone plugs or bone blocks at both ends of this newly constructed ACL which can be beneficial when anchoring this new ACL to the femur and the tibia But just like the hamstrings you can have some cons with this graft Often people will have anterior knee pain that can sometimes last over a year postsurgery People can also be at an increased risk of patellar fractures and even patellar tendonitis And coming back to the hamstrings another con of taking this uh tendon or this graft from the semi-endinosis sometimes people can have a decrease in hamstring strength at least initially after surgery A lot of times especially athletes and people who are dedicated to their physical therapy can regain most of if not all of that hamstring strength And even this semi-tendinosis tendon has been known to regenerate to a certain degree But what about a donation or a cadaavver ACL cadaavver ACLs or ACLs from a body donor or a cadaavver are referred to as alogors and those most commonly actually come from either the Achilles tendon or again that patellar tendon They sometimes can come from like a hamstrings tendon or even a tendon from the tibialis anterior muscle But just like those autographs these alligraphs or these cadaavver ACLs are going to have some pros and cons A pro would be you're not pulling tissues from your own body So you won't have any postsurgical pain like in your hamstrings or in your patellar tendon But there is a small increase in risk when you're getting an alo graft rather than taking tissues from your own body And these tend to have a higher reinjury or re-rupture rate when you're comparing them to the autographs So what about preventing an ACL tear is there anything that you can do to reduce your risk well it appears that according to research you can reduce your risk with incorporating neuromuscular training into your routine Neuromuscular training is essentially used to improve the communication and coordination between the nervous system and your muscles And this would include things like plyometrics which if you haven't heard of plyometrics before these are exercises that include rapid explosive movements that really train your nervous system to recruit muscle fibers effectively and quickly which will improve muscular power agility and coordination All of which are important for preventing ACL tears Neuromuscular training also includes landing drills because if someone were to practice landing over and over and over again with proper form that will almost make landing properly automatic during sporting events and again lead to a decreased risk of ACL tears Balancing exercises are also another large part of neuromuscular training and even good old-fashioned strength training especially when it comes to balancing your anterior chain with your posterior chain or in other words balancing your quadricep strength with your hamstring and glute strength The bigger the discrepancy that people have between their quads and their hamstrings the greater the risk Or in other words when somebody is very quad dominant and has weaker hamstrings this makes this individual more prone or more at risk for an ACL tear because the hamstrings aren't effectively able to prevent that anterior translation of the tibia So you most definitely want to have a balanced strength training protocol for those opposing muscle groups There is some research that shows a proper neuromuscular training program can reduce ACL injury risk by over 50% So this obviously can be greatly beneficial and honestly a lot of people are already doing some of this neuromuscular training as part of their routine Like a lot of you are probably already doing some strength training and even possibly some agility drills And so just adding a few extra things like I do some light plyometrics and landing drills as part of my activation and warm-up prior to playing basketball a few times a week You could also throw in some balancing drills during your lower body strength training days So in other words it wouldn't take a lot of additional effort to incorporate a few extra drills to help protect your perfect little anterior crucet ligament