hello everybody and welcome back to another anatomy tutorial today we're going to be having a look at the anatomy of the knee specifically looking at the mri anatomy in the coronal sagittal and axial planes i'm going to show you how to identify some really clinically important structures and then head through each scan in a real systematic way looking at the bones the ligaments the menisci the articular cartilages some of the muscles that cross the knee joints identify some of the fat pads surrounding the knee joint as well as assessing the extensor mechanism of the knee so let's start by having a look at this coronal image here this is a coronal pd of the knee and the first thing we need to do is figure out which part of this image is medial and which is lateral the first clue that this is potentially medial is this thick band this homogeneous band that comes all the way down here low signal band coming in close contact with the meniscus here and this is the classic appearance of our medial collateral ligament then if we scroll slightly posterior in the image we can see almost the profile of a face here you can see the neck coming up to the chin the nose the forehead there this is a classic appearance of the lateral posterior portion of our lateral femoral condyle again another clue that this is potentially lateral and then of course if we see our fibula coming into the image we know our fibula lies laterally and we can say confidently that this is our lateral portion of the image so let's have a look at our femur coming in at the slight angle here we can see our medial condyle of the femur and our lateral condyle here and then that articulates with the tibia we can see our medial tibial plateau our lateral tibial plateau and then we can see our two tibial spines our medial tibial and lateral tibial spines there again we can go back and see the fibula here we can see the styloid process of the fibula the head the neck and then follow that right down into the lower leg so let's identify some of the ligaments that surround the knee we've already looked at this medial collateral ligament just a single ligament coming along that side our lateral ligaments are a little bit more complex they're actually four structures that make up our lateral collateral ligament complex we can head slightly anteriorly we can see our it our iliotibial band coming and attaching to this tibia here as we head out posteriorly we can look at our fibula head and see a structure coming off the fibular head up into our biceps femoris muscle this is our biceps femoris tendon coming all the way down attaching to the head of the fibula as we look at the head of the fibula we see another structure coming up here and attaching to that face that we saw earlier now from this like nasal bridge area if we follow it down we can see this ligament coming in attaching to the fibular head this is what's known as our fibular collateral ligament and the last structure that makes up the lateral collateral ligament complex is quite difficult to see on these coronal planes and i'll show you them more closely on our axial planes but it's our popliteus tendon that's going to come around here coming down you can see it here and into our popliteus muscle here so we've got four structures on that side the proper ts tendon our fibular collateral ligament our it band as well as our biceps femoris tendon coming all the way down those are our four ligaments there are four main ligaments there let's head now into the joint itself we can see a ligament coming from here we're anterior on the tibia as we head down posteriorly we see that ligament heading all the way backwards attaching to this medial surface of our lateral femoral condyle this is our anterior cruciate ligament following it all the way there we can see there's some heterogeneous signal within this ligament which is normal and we can see slightly here that there's almost two bands coming here we have an anterior medial band and a posterior lateral band of our acl ligament so we need to follow this ligament all the way down from its attachment at the tibia all the way up to its attachment at the femur here we can see if we go anteriorly we can see this is our pcl our posterior cruciate ligament and it's called posterior because it attaches to the posterior segment of our tibia so let's follow that ligament all the way back back back back we can see it attaching here to the posterior tibia and we're going to see this in both our sagittal and our axial planes as well perfect let's move on to the menisci now sometimes it's easier to look in our fat set images because we get a better a better detail of um in this guy here we can see the meniscus is this triangle shape we have our base of our meniscus here which is not an articular surface and then we have these two articular surfaces here of our meniscus you can see a nice sharp angle here now when we're looking for tears by definition there needs to be disruption of the articular surface of a meniscus so you can see how there's a white line within this meniscus that's not a tear it doesn't actually reach down to our articular surface now both menisci are bound to the tibia by an anterior and a posterior root then they head off into the horns of the menisci the body of the meniscus another horn anteriorly and then back onto its roots and i'm going to show you how to identify those structures now so let's start anteriorly on this medial meniscus we can see here the attachment to the tibia is our anterior root of our medial meniscus let's follow that round this is our anterior horn of the medial meniscus coming into our body the body heads all the way back before curving around into our posterior horn of the medial meniscus and then attaching at the posterior root here again we're going to look at these as well in the sagittal plane let's look at our lateral meniscus i'm going to start anteriorly we can see our anterior root coming into our anterior horn here going back into the body of the lateral meniscus round to the posterior horn of the lateral meniscus and attaching more medially here as our posterior root of that lateral meniscus while we're here we can have a look at the articular cartilage here start by scrolling through this medial articular cartilage of the femoral condyle and we want to make sure that the cartilage is not disrupted there's no bits of cartilage that have broken off we can also look within the joint space to see there aren't any inter-articular bodies there that may be signs of bits of bone or bits of cartilage that have broken off and we want to do this on both sides we want to see this cottage maintaining its thickness being nice and smooth we can see that this cartilage has got a black line underneath it it's a bit clearer on our coronals here we don't call this black line cortex as we would do further up this is our subchondral bone plate here so we want to make sure again on the tibial plateaus that we maintain the integrity of our cartilage we look at that on both sides there perfect so we've identified the bones we've looked at some of the ligaments we've gone through our menisci as well as looking at the cartilage let's move on to our sagittal image again the first thing we need to do before we label anything is figure out where is medial and where is lateral so the first thing we can do is have a look at the shape of the tibial plateau here and if we've got this convex shape here it looks like a golf tee side on a golf ball would be sitting on top here that's a classic shape of our medial tibial plateau and again if we were to scroll through that medial plateau we wouldn't see any fibula there as we head out laterally we can see that we have a convex superior pole of our lateral tibial plateau and obviously we'll see a fibula here which is indicative that we are lateral so we'll scroll through those bones we must we can also have a look at the patellar bone here as we can scroll through now sometimes the patella is divided into two portions a bipartite patella or sometimes even more a multiparty patellar those are both normal anatomical variants you mustn't be tricked by that and call that a patellar fracture we can look at our extensor mechanism here we've got our quadriceps tendon coming down to our patella and we can follow that patellar tendon then all the way down to our tibial tuberosity on the anterior surface of our tibia here we want to make sure that this got low signal all the way through nice thick bands and there's no disruption of that extensor mechanism let's have a look at some of our ligaments now it's quite difficult to identify our collateral ligaments because we don't always catch them in plane but let's come out laterally we can see that our biceps femoris tendon we actually catch that in the plane here as well as our fibular collateral ligament coming down there so that's not always seen but you can see it here obviously our it band is too thin we haven't caught that and it's quite difficult to see how poplar tears tendon but we can see it coming around posteriorly here and as we head down we can see our popliteus muscle back there then let's look at our cruciate ligaments it's a great way to assess them here in the sagittal plane we want to come to our intercondylar region here and we can see our acl coming it's a nice steep angle this acl's gradient must be much steeper than this gradient here our intercondylar grain gradient to our bloomin starts line so we can draw a line across here that gradient should be much less than our steep acl coming through here we want to scroll through that acl make sure we follow it all the way it's attaching to both the tibia and the femur again we've got this heterogeneous signal here we can look at our pcl attaching posteriorly to the tibia it's a much thicker band low signal all the way through hooking around like this and attaching to our femur on that side we also want to scroll through it make sure we've got attachments on both sides and our pcl prevents our femur from tracking forward and if you think about how often when we're jumping or landing that we're actually in a bit of a flex position here you can see why the pcl needs to be much stronger than that acl because our femur is always having pressure forward like that whenever we've got a bent knee and we're weight bearing our femur wants to slip forward and we need a strong ligament to prevent that femur from slipping forward let's have a look at him in this guy i'm going to start here at our anterior root of our medial meniscus i want to follow that all the way around in our anterior horn now as we carry on following that round we should see our body of our medial meniscus and then heading into our posterior horn of our medial meniscus following it around to our posterior root just before our pcl here then we can see our pcl come into view and what we can also see is our acl coming down now acl comes in real close proximity to the anterior root of the lateral meniscus so we can see here our anterior root of the lateral meniscus coming around into our anterior horn again the whole way through we need to assess are these articular surfaces intact is there any disruption with that but here there's none is minuscule normal we're into our body of our lateral meniscus and again then we can follow our posterior meniscus all the way back down posterior horn of our lateral meniscus and our posterior root coming down and attaching to the tibia here just a word of caution when you're in your posterior root of your lateral meniscus we can see our poplitease tendon coming up here and sometimes there's a little bit of white here high signal which is actually our properties recess and that's not a disruption of our meniscus that's just a space between the poplitease tendon and our lateral meniscus our posterior horn of our lateral meniscus we can also see here the fat pads we've got our infra patellar fat pad here otherwise known as our hoffa's fat pad and then above the patella our supra patellar fat pads you can see we've got an anterior suprapatellar fat pad and a posterior suprapatellar fat pad this is also known as a pre-femoral fat pad what we can get is fluid actually tracking up when we have a joint effusion fluid can track up and separate those two fat pads and you can often see that on an x-ray you'll definitely see it on an mri especially if you've done a sagittal pd here a fat sat you can see fluid is bright fat is now dark you can see how fat is now dark you can get fluid tracking up and separating that anterior and posterior suprapatellar fat pad okay let's head on to our axial slices again we need to find out where's medial where's lateral the first clue here is our patellar facet here has a longer portion this is our lateral patella facet and the shorter portion here is our medial patella facet you can see there's actually another little facet here that's known as the odds facet and doesn't actually articulate with anything but we will see that in many patients we can see our patellar retinaculum medial and lateral here preventing the patella from dislocating laterally so now we can see we're at the level of the femur there's one single bone another clue that this is medial is we'll get to know these muscles here they lie medially we know this muscle here this is our biceps femoris we can follow that down we should see the biceps tendon biceps femoris tendon forming and attaching to our fibula here which we see as we come up we'll see a small ligament here our fibular collateral that we covered earlier it's nice and rounded like that and sits slightly anterior to that biceps femoris tendon and we can follow that all the way up attaching to the femur here we can also follow our poplitease tendon coming down and back around to our popliteus muscle which lies anterior to our popliteal artery this is our gastrocnemius here and we can see that there's a medial and a lateral head now the medial head of the gastrocnemius has this large tendon here and this is our semi-membranosus tendon that attaches here posteriorly we can follow that semimembranosus there all the way down attaching as we follow it up we can see there is our semimembranosus and then we have three muscles here s g t i think of it as sergeant we've got our sartorius our gracilis then our semitendinosus so we can see our semimembranosus coming down and attaching there we can see our gastrocnemius let's have a look at our collateral ligaments so we start up in the femur we should see medial surface here is our medial collateral ligament we can follow that down it sits very close to the meniscus here and then heads down into the tibia and it touches down posteriorly we've looked at our biceps femoris tendon we've looked at our fibular collateral ligament as well as our poplitease tendon the last structure we need to find here is our it band which then also goes down and attaches as we head down attaches to the tibia here we can see this thin it band up here let's look at our cruciate ligaments we can see our acl heading anteriorly fans out there before attaching to the anterior surface of the tibia and then we can follow our pcl coming from the posterior surface of the tibia all the way up following it following and attaching to the lateral surface of this medial femoral condyle there if we can follow that tendon all the way down make sure it maintains its integrity like that and then looking at the acl coming across and fanning out can't really see the two bundles here but we want to follow it all the way down let's talk about these three muscles here so we've got our semitendinosus our gracilis and our sartorius they run around and uh attach it out pes and psorinus we actually don't get all the way down here but this is an important area we can get a fluid accumulation there and then another really important area i was showing you the semi-membranosis here right adjacent to this medial head of the gastrocnemius if we get fluid building up separating those two from each other this is what's known as a baker's cyst which i'm sure you've heard of before as you can see here we've just managed to cut the lateral meniscus in plane which is not always the case but you can see how the lateral meniscus is this tight c-shape and it's difficult to see here but we have our posterior root our posterior horn our body anterior horn coming to our anterior root and our medial meniscus is much broader much wider and the roots are not as close to each other so we've got our posterior root posterior horn into our body coming around to our anterior horn and our anterior root at the front there it's not too easy to see but you can see the shape difference of our lateral and medium in the sky lastly we can just have a look at our quadriceps tendon as it's coming down you can see our patella there now you might see that there's no cartilage here and there is on the patella and that's because if we look at our sagittals here the cartilage on the patella comes much before the cartilage on the femur and so that's normal we mustn't be scared that we're now missing chunks of cartilage on the side we should follow it down the cartilage then oppose we should see them nice and thick maintaining their thickness no chunks of cartilage missed head further down further down we can then see our patellar tendon heading down towards our anterior tibia there so follow that up make sure we've got low signal tendon all the way up to our patella we've got a whole patella there and into our quadriceps tendon so that's it we've covered the basic structures of the knee on mri i hope you've managed to follow along it can be a bit confusing but as always i'm linking the case below go and have a look for yourself scroll through the images try and label as many things as you can and when you're looking at these scans in real life in actual clinical practice make sure you're questioning is this normal every time don't just go through the motions of identifying the structure ask yourself does this look normal and if not then try and figure out what's going wrong so i hope you've enjoyed it let me know what other anatomy videos you want to hear about next and i'll see you in the next video goodbye everybody