 Hello and welcome to noon conference hosted by MRI online noon conference connects the global radiology community through free live educational webinars that are accessible for all. And as an opportunity to learn alongside top radiologist from around the world. We encourage you to ask questions and share ideas to help the community learning grow. Today, we are honored to welcome Dr. Donald Resnick for a lecture on meniscus of the knee function and dysfunction. Dr. Resnick is a renowned lecturer and his list of dozens of awards and honors include a twice awarded most effective radiology educator from ant mini. 2018 ACR gold medal for his lifetime achievements and an honorary doctorate from the University of Zurich. We're thrilled he's here today to share his expertise with us. At the end of the lecture, please join Dr. Resnick in a Q amp a session where he'll address questions you may have on today's topic. Please remember to use the Q amp a feature to submit your questions so we can get to as many before our time is up. Dr. Resnick, thank you so much for being here today. Please take it from here. Thank you very much. It's a privilege for me to be here and to share some information with those of you listening. I'm coming to you from my home in Del Mar, California. Currently it is dry. It was wet about a few days ago when we have a large storm pass through this area. Today I've chosen the topic meniscus function and dysfunction, because I think for those of you doing MR imaging. Of sports medicine injuries, the knee and specifically meniscal injuries represent a large part of what you are doing. So, there are two particular objectives for this lecture. We're listed here. I'm going to review meniscal structure, pathophysiology with emphasis as I'll show you on the collagen framework that is found within the meniscus. And then knowing that framework, we're going to look at classic patterns of meniscal failure of which there are three. And I'll try to explain why they look as they do on the MR images. And here's a little point for you when you see this guy, pay attention to what is written here. You're going to see him maybe four or five times during the lecture. He'll be smaller than this. So be at the bottom left part of your screen. So keep an eye out for him. And when you see him, please pay attention to what's written on this particular item. So let's start with a few general features. Okay. And what I would like to say at the very beginning, I want to emphasize the similarities between things we call articular discs. For example, the triangular fibro cartilage disc of the wrist shown in the middle on your right. The menisci of the knee and the labra, as you know, which we see typically in the hip and in the glenium will join. These structures have similar tissue. It's transitional tissue between fibers connected tissue and highland cartilage. These structures are poorly vascularized and in general the vascularity is more prominent in the periphery than in the central portion. And all of these structures undergo age related degeneration and sometimes degenerative failure that can lead to full thickness perforations or tears. And these are trauma related abnormalities and we're going to be emphasizing some of those today can lead to clinically significant findings. Now just a word at the beginning, at least if you go to an anatomy book and try to define the difference between a meniscus and this you will see that a meniscus partially divides a joint cavity. As you can see on your right and a disc completely divides a joint cavity. It contains those particular articulations that have either a meniscus or a disc. The problem with that definition is with aging. A disc may develop a full thickness perforation and then indeed it is a partial division of the joint cavity that results. So there's a little bit of confusion with regard to the terminology. To understand pathology, you have to understand anatomy so let's look briefly at the meniscal anatomy. You're the femur you're looking down on the top of the tibia the media meniscus on your left, the lateral meniscus on your right. The first thing that is obvious is that the media meniscus is more elongated and the lateral meniscus is more circular. In contrast, the lateral meniscus covers more of the lateral tibial plateau than does the media meniscus of the media tibial plateau and the lateral meniscus absorbs more axial load than does the media meniscus. Now this drawing done number of years ago has other structures on and I'm going to emphasize four of them and they're labeled for you 123 and four because we're going to talk about those structures later on in the lecture. These are the root ligaments to our anterior that's numbers one and three to our posterior that number two and four to are related to the media meniscus to are related to the lateral meniscus and the one we're going to emphasize is the one mark two on this drawing the posterior root ligament of the media meniscus. Well, let's not skip ahead to that let's go first with the meniscus. If you look at menisco composition you can see initially as shown in the yellow boxes it is a well hydrated structure of the organic matter representing 30% of the wet weight. I put an arrow next to collagen because it's the collagen that I want to emphasize today. It's a major component of the meniscus, and it transmits the force extending through the meniscus. In general, if you go to anatomy books you will lead and find out about the menisco functions, the five major ones are listed here. The meniscus can serve to protect our tick of the cartilage it absorbs shot. It transmits load. I show you a section of the knee at the bottom right, showing you that the meniscus are protecting the adjacent articulate cartilage. Note all the abnormalities in the uncovered portion of cartilage but not in the part covered by the meniscus. The other point I would make about menisco function the menisci generally are not considered primary stabilizers. But if something goes wrong with a primary stabilize a stabilizer. The meniscus may in fact assume an important stabilizing effect. And the one I'm going to talk about later is what occurs to the posterior horn of the medial meniscus, when there is failure of the anterior cruciate ligament. Because you see in that situation, the posterior horn becomes a resistance to enter translation of the tibia and a peculiar pattern of failure does occur in the posterior horn of the meniscus, known as a ramp lesion. More about that a little bit later. I was a first year medical student, when I learned that the menisci were largely a vascular, not entirely a vascular but largely a vascular. There are actually are two sources of blood supply to the meniscus their number here one and two for you. And if you look on the right at the top image, you can see the number one and number two. Number one is a Perry menisco capillary plexus number two are the synovial reflections adhering to the top and bottom of the meniscus and as you look at my drawing and you look at the section below it. You can see that the vascularity involves the peripheral aspect of the meniscus and not the larger or wider central portion. The orthopedic surgeons offer refer to this as the red and white zones of the meniscus failure in the red zone can indeed be associated with spontaneous correction of the failure that is the tear may heal, or the surgeon may elect to go in. When you have failure in the white zone, we run into a problem where a reception of the damage meniscus may be required. So slide on your left showing you a red zone tear in the vascular portion a probe is showing you that in at the bottom of that image. Now in order to understand hairs you have to understand normal menisco morphology. So what I've done here we're looking down at half of the TV and I'm showing you three parts of the media meniscus. The posterior horn at the bottom the anterior horn at the top in the distance. Now what you need to know about the media meniscus is its width. Based on the literature the widest part of the media meniscus is the posterior horn. The mid portion by the way can be very narrow, although sometimes it is not but the posterior horn is the largest part. The work way to survey the integrity of the media meniscus on sagittal images is to compare the width of the posterior horn to the width of the anterior horn. And in general the posterior horn should be wider if it is not, there's a problem, and we'll talk about what might be the causes for that a little bit later. If we do the same experiment on the lateral side the results are different. The widest portion of the lateral meniscus tends to be its mid portion or body with the posterior horn and anterior horn being similar in width. So a quick survey of the integrity of the lateral meniscus on a sagittal image shown here is that the width of the posterior horn on your right should indeed be about the same as the width of the anterior horn on your left. Okay, this is a critical slide. There's a lot of information. Let me see if I can simplify it for you. There's a beautiful image at the bottom left showing you indeed the collagen framework of the meniscus. There are two types of collagen bundles found within the meniscus. The first of these I'm showing in the here as these blue bundles. Here the arrow is pointing to them. These are longitudinal circumferential collagen bundles. They are found mainly in the peripheral 50% of the meniscus and they run in circumferential direction. So in simple terms, they connect the anterior and posterior portions of the meniscus. The second type of fibers are known as radial tie collagen fibers. If you show them as the orange arrow and these orange arrow heads, they run in from the periphery all the way to the central portion. You can see in the bottom right, radial tie fibers, beautiful specimen images. So what I'll do and I simplified it at the top right, I'm showing you the longitudinal circumferential collagen bundles in red cylinders, connecting the anterior and posterior portions of the meniscus. And I'm showing you radial tie fibers in white connecting the peripheral and central portions of the meniscus. And that's all you need to understand to realize the patterns that may occur with menisco bearing. Now there are classification systems. The icicot system listed here has seven characteristics that they feel should be described at the time of surgery. And many of these characteristics are part of our description when we are looking at MR images of the knee. I'll comment on some of these as we go through this lecture. Now they're all kinds of patterns of menisco failure. But the three basic ones are labeled here one, two and three. And we're going to be talking in detail about them. Longitudinal vertical tears, number one, horizontal or longitudinal horizontal tears labeled number two, and radial tears labeled number three. Those are the three basic patterns of failure. Now to understand why the meniscus fails you have to understand something called hoop stress. And indeed it's hoop stress that's led to failure of the Liberty Bell in Philadelphia. So this is a sagittal section from the posterior form of the media meniscus and I'm showing you now the femoral force coming in with axial loading at an angle. Now if you remember how we deal with vectors we can divide that force into a horizontal vector that's this arrow and a vertical vector that's this arrow. The tibial force is a vertical force that counteracts the vertical force on the femoral side. So what is left unopposed is this horizontal force, which leads to a pattern of trying to drive the meniscus from the joint that pattern of stress is known as hoop stress. There are other patterns including circumferential stress that try to drive the meniscus posteriorly and anteriorly but it's a hoop stress that is the major cause for meniscal failure. So I drew last week kind of a blue triangle of a meniscus showing you here's the hoop stress, extending to the periphery and the major counteraction to that are the longitudinal circumferential fibers. And the circumferential force here, moving anteriorly and posteriorly and the major resistance to that are the radial high fibers. It's of interest, although I won't go into detail that these three basic patterns of failure are delaminated tears at least in part, because they are parallel to some of the collagen bundles present within the meniscus. And as you can see in tendons and in ligaments delamination failure of the meniscus occurs. Now we come across as the radiologist it's our job to diagnose meniscal tears. And as you probably know if you're doing MR of the knee there are two classic meniscal findings of a meniscal tear. I've numbered them there and abnormality of meniscal contour, and an abnormality of meniscal signal, as I'm going to show you one of these is terrific. And the other is a terrible finding that is not very reliable. The normal meniscus tends to be smooth and triangular of generally low signal. The first alteration that we look for is an abnormality of meniscal contour drawn here. It can be truncated it can be irregular. Any of those findings would represent an abnormality of meniscal contour. I'm going to talk more about that in a moment. The second criteria is an abnormality of meniscal signal with a classic teaching be it that if you have altered signal, be it gray or even bright like fluid that violates the top, the bottom or the apex of the meniscus. It's evidence of meniscal tear, the periphery of the meniscus does not count as a meniscal service. The first criterion and abnormality of meniscal contour is simply terrific. If you can eliminate the possibility of prior surgery. Now I can tell you, sometimes the surgeon tells you on the request slip there has been surgery. Sometimes he or she does not. But worse, sometimes they tell you there's surgery and there never has been. So the first thing I always look at when dealing with MR or the knee is evidence for prior surgery or throstomy and I look for scarring. And we have found the best place to look for scarring is the antromedial portion of the knee far more than the antrolateral. If you have scarring and haphaz fat pad you're looking in some cases top left, you may even get a cyclops lesion, where you're looking for things like thickening of the ligament of mucosum within haphaz fat pad. There's one type of scarring or fibrosis that may be significant. And there are reports that indicate that if you have fibrosis in the enter interval of the knee and I show you that what that is in my section sagittal section of the knee is pretty much all of haphaz fat pad that if you have fibrosis particularly in its deep portion as shown here. It's associated with pain anteriorly in the knee, typically on extension there may even be a flexion contracture. So when I see extensive fibrosis in the enter interval I mentioned the second criteria and an abnormality of meniscal signal is simply overrated. The results are inconsistent. Now you remember the history of this in the 1980s and 1990s. The grading system was introduced looking at signal within the meniscus. Grade one might have a little bit. Grade two had more extensive but it didn't violate the surface. Grade three violated one of the surfaces of the meniscus. Typically normal menisci have no signal or grade one degenerative menisci were reported to have grade two signal. And when you got to grade three, you were dealing with a meniscal tear now that sounds terrific, but it doesn't work so well. So here you can see at the top white what might be grade one or two no tear and grade three at the bottom the tear and the difference here is maybe a couple of pixels. So what I have found through the years is that the resident or fellow gets a very, very close to the computer screen. You're going to make that last pixel bright to change a grade two to a grade three and no even use if you look at the image at the top, meniscal window it to get that to go out to the surface of the meniscus. In short, you should be able to sit comfortably in your chair like this. It should be obvious at a distance. And indeed it's my view if you're not sure it is better to under call than to over call a meniscal tear. Clearly in some cases signal that initially was inside the meniscus look at the top row might later here five months later become obvious grade three signal or meniscal tear. So the patient can come back for a second scan, if the pain is persistent. So I tend to under call not over call and indeed, another type of thing that was suggested is something called the two slice touch rule to make this second criterion more reliable, the idea that if you saw disruption of the surface of the meniscus and more than one image, either in the same plane or in multiple planes, their variations in the reports of this that it improves your diagnostic abilities. And you can see some data provided by the people at Wisconsin that shows indeed that to slice touch increase the reliability the positive predictive value particularly for the lateral meniscus. Right, we're ready now for the basic tears. So with compression of the meniscus we're going to see our first tear a longitudinal vertical tear. What occurs with compression is hoop stress. So the initial pattern of failure related to this sort of loading is a micro tear that is along the axis of the hoop stress watch the image now I'm going to put it in here. And as it goes in encounters longitudinal circumferential college and bundle, and it stops the micro care. The tear continues along the path of least resistance as a longitudinal vertical care longitudinal or circumferential because it has a circumferential dimension, vertical because it is vertical or vertical blade. These tears may occur in younger people following injury and you see them in the outer half of the meniscus, where you have these college and bundles. Here's my transparent meniscus I'm going to draw a long longitudinal vertical there in yellow, the longer it is, the more radio type fibers that are violated and what do they do. They tie together the central and peripheral portion. So when you have a long vertical tear, you may end up with a situation where the central portion displaces more sensually. You have a bucket handle pair of the meniscus a bucket handle pair then a displaced longitudinal vertical pair. Let's go ahead and image one. Here is the tear peripheral half of the meniscus. The length of a longitudinal vertical tear is its circumferential dimension. So here's our first image. This is a complete one that goes from the top to the bottom. Let's stay in the same plane. We're doing that now. And its appearance is identical. It's a boring finding. And by identical not that it vertical or complete but also it's at the same distance from the periphery of the meniscus, because it is paralleling those collagen fibers the path of least resistance. So when you look at these tears here's the first image, the second image, the third image they look the same the fourth image. Knowing the thickness and spacing you could figure out the length of a longitudinal vertical pair if it's over nine or 10 millimeters, it may in fact be unstable that is something that has been reported. And that ramp lesion is something whose definition has changed through the years, typically associated with enter, cruciate ligament failure, be it now acute or chronic, because now enter translation is resisted by the posterior horn. A peripheral vertical tear or tear, sometimes they're multiple, occurs at or near the meniscus capsular junction. So here's a beautiful example of one. This was in a patient with ACL deficiency. You'll note one of the characteristic findings that I always look for. Not just the altered signal in the periphery but look at the tibia. There is marrow edema and that's often found when dealing with peripheral failure of the posterior horn of the medial meniscus in patients who have ACL problems. Okay, pair number two longitudinal horizontal pair it's known also as a cleavage there. Seen an older people horizontal in its appearance, often associated with menisco degeneration. It relates mainly the sheer force. This terror begins at or close to the apex and takes the path of least resistance, going between these longitudinal college and bundles. And sometimes I showed in the example, and in my drawing on your right, because of so many of these bundles out in the periphery, there may be branching of this particular pattern of menisco failure. So this is the cleavage here and often it divides the meniscus almost into two equal parts at top and a bottom. Here's what it looks like in my drawing. All right, we're going to go ahead now and show what happens when the terror becomes large. It opens up like a fish mouth. The length of a longitudinal horizontal tear relates to its circumferential dimension. The width relates to its central peripheral dimension. And indeed, it is these tears that are often associated with power menisco gangly insist. Classically, we're taught that those power menisco gangly insist are bright because fluid from the joint is passing through the tear and entering the cyst. But sometimes it's bright because of new sin is degeneration, not joint fluid, new sin is degeneration in the meniscus and also within the power menisco cysts. Now just a few words about these power menisco gangly insist. They're more frequent media. They are larger media. The medial cysts are more aggressive. The association with menisco pairs is higher on the medial side and bone erosions, although rare may occur. So you can see in my drawing and in this particular example these are aggressive lesions medially. They may extend the medial aid or extend around the medial supporting structures as shown on the right. And another interesting thing is when they occur adjacent to the posterior horn of the medial meniscus. They may extend centrally becoming located behind the posterior cruciate ligament. So if you don't know this, you're going to call this a power cruciate gangly insist. The meniscus go back to the posterior horn to see if there's a tear and a power menisco cyst. Now if you have a tall meniscus, let's think of a discoid meniscus. Shear forces can be extensive and a pattern seen particularly in a discoid meniscus is known as central cavitation saw criteria change. So if you have a discoid meniscus with a lot of gray signal as shown here, even if it doesn't violate the surface of the meniscus often it is found to be cavitary at the time of our frost could be. So this is intra menisco parent. I'm not going to be talking about discoid menisci in this lecture, but I can tell you the patterns of failure in a discoid meniscus are very different from the patterns of failure in a non discoid meniscus. Okay, we're up to the third basic type of tear the radial tear. This is not a longitude nor circumferential pair. This is a tear that also starts from the apex and extends to the periphery, but it is unique watch my drawing. I'm going to draw you one now here it comes. And as it goes out to the periphery, it violates those longitudinal circumferential college and bundles. That's shown nicely in my drawing on the right and you can see that nicely, as this tears extended all the way out to the periphery of the meniscus, the bottom image shows that. So ahead to my transparent meniscus, you can see a long radio pair in yellow. The length is its central peripheral dimension. It parallels the radio type either shown in white in the distance. The longer this pair, the more of those red longitudinal circumferential college and bundles are disrupted. They tie together the enter and posterior horn so a long radio pair is associated with opening up of the meniscus like a book, producing a meniscus gap which should be measured if you can on the MR images. Now I can tell you I wasted 20 minutes of my life on the case you see on the right. Because you see I didn't know all this when this case came through a few decades ago. And when I saw this image I said oh my gosh is a menisco fragment somewhere in this joint. And I spent 20 minutes trying to find it didn't find it, because there is no fragment this has opened up like a book, very very characteristic pattern that occurs with large radio pairs. I don't know the disruption of the bow tie that occurs with radio pairs even those that are small. You can see a normal bow tie top image on your left and the disrupted bow tie. And you can see that on the MR image atop right, and here in a specimen showing you two areas that a radio pair or tears has disrupted the bow tie. So let's go ahead and image this radio pair and if we image it through the gap. We see an absent or empty meniscus. The bottom left shows you the case where the anterior horn of the media linus it's not a pretty image but you can see it. Here's the gap. There's no meniscus here that's the gap related to the radio tear. The single or multiple radio pairs are characteristic of failure of a discord lateral meniscus. So it's another pattern of failure that we see with discord meniscus beautiful example shown here. The parrot be tear is a displaced radial tear called that because the shape of the beak of the parrot. It's curved so let's go ahead and see what happens when we image this terror. Here's my first image. And what do we see a longitudinal vertical line in the inner half of the meniscus. What I think that's made is to call this a longitudinal vertical tear. They occur in the outer half, not in the inner half. And let's image it again in the same plane and in this case, that longitudinal region is marching toward the apex. This is called the marching clefson. It may march away it may march toward depending on the exact pattern of failure. It's characteristic of a radial tear particularly a parrot beak type of radial tear. So here I'm showing you a case. The red picture is that of the torn meniscus you can see there I'm imaging it. Three sections in the sagittal plane a B and C. And here we see there a marching cleft that goes all the way out to the periphery in this case. This is not a longitudinal vertical tear. This is a parrot beat radial tear. Okay, another critical slide. The normal sagittal appearance of the posterior horn of the media meniscus is shown in the bottom right. This is my central image that's the posterior appreciate thing in it. The next image shown here should show a significant amount of meniscus we're moving medially. And the next medial image should show the entire meniscus that's normal. Here's my case. There's the central image and then my next image similar to this is virtually nothing. But that's abnormal. And that's an abnormality of the posterior horn of the media meniscus or as we'll talk about in a couple minutes, the posterior root ligament. So don't be surprised in a case like that if you get a coronal image, and you see indeed that abnormal space. The normal posterior horn will curve down as the posterior root ligament of the media meniscus. A couple of years ago, I got a call from one of our prior fellows who said, gee, I really enjoyed my fellowship they all start that way. And then he said, you know, I'm really successful. I'm doing a lot of MR images of the knee I want to shorten the examination, and you shorten it to one sequence. I can't recommend that. But if I had to shorten it to one sequence, it would be the fluid sensitive often fat suppressed coronal sequence shown in this particular image. Because it shows ligaments it shows contusions and fractures, and it shows you some information about the meniscus. And he got back to me and said, you don't understand I'm really successful. Can you shorten it to one image. I say, you know, I, I can't recommend that. But if I had a short knit to one image. It's the image you're looking at. This is the most important image of an MR examination of the knee. It's the coronal fat suppressed image and what you want to look at, look at because of the frequency of problems here is this area. Spend 10 seconds at least, looking at this image. I'm going to go a step further. Here's the single most important one half image of a knee MR examination. Always spend time on this image. This could be a radial tear of the posterior horn it could be a posterior root ligament evolution, more about that in a minute. Now there are tensile failure patterns of the meniscus. I'm going to show you two. One of them relates to problems with the medial supporting structures and there are a lot of them. I'm just showing you some in this kind of coronal drawing. The tibial collateral ligament, the menisco femoral menisco tibial ligament. When you have a valgus injury, tensile force is placed on the meniscus, often the body of the medial meniscus, sometimes the posterior horn. And what occurs is a corner pattern of tensile failure. Here's what it looks like by drawing. And here's what it looks like by Emily. We can see with a blue arrow. There's a problem with the deep medial menisco tibial ligament. You can see a little edema where it attaches to the tibia. And the arrow is showing you that corner failure. May not look like much, but look at my drawing. This is going through some longitudinal circumferential college in bundles. The second pattern of tensile failure occurs related to one of the arms of the posterior oblique ligament of the knee. Now I'm not going to get into detail today about the anatomy of this very important ligament other than to indicate, classically there are three patterns of fibers within it. The largest one and thickest one is known as the central arm. And it's shown here between the blue arrows and here taken from the literature by Le Prad. You can see that arm. That arm attaches to multiple structures, including the posterior horn of the medial meniscus. A corner pattern of failure may be seen typically of the superior corner of the posterior horn of the medial meniscus again related to valgus injuries and failure of the medial supporting structures. There are three classic patterns of displaced menisco pairs. The bucking handle we've already talked about the displaced longitudinal vertical, a displaced longitudinal horizontal tear is a flap tear. Now, I want to remind you a flap in English means attached at one end, a fragment means it's not attached at all. Menisco fragments are rare. Menisco flaps are common. Often we'd launch it to no horizontal failure. Here's a displaced flap extending next to the medial portion of the tibia and you can see an erosion of bone. And there's some fluid in the medial collateral ligament person. The parrot be tears we've talked about is a displaced radial tear. Some type of bucket handle tear that's known as a hemibucket handle pair. It can be a tough diagnosis, typically associated with longitudinal horizontal fail. You can see here, I'm showing you two cases here's the failure and that's half of that meniscus that part that's a flap located centrally and here's a very similar case on your right. It's known as hemibucket handle tears, because the peripheral portion that remains tends to be quite wide and the abnormality the tear may be difficult to identify. Okay, we're going to finish up in the last five or 10 minutes with a couple other aspects of menisco failure we're going to go to the root leg. You know, 20 years ago there was virtually nothing written about menisco root ligament tears. And while these tears occupy a large part of what is being written about the menisci in the literature. It is suggested that root ligament tears account for maybe 10 or more 15% of menisco findings at the time of our philosophy. The root ligament of the media meniscus is most frequently involved. I'm showing you images of it here on your right. Other root ligaments, particularly on the lateral side may be involved in patients who have ACL tears I'm not going to emphasize much about that today. And these ligaments have both central and supplementary fibers, so they may have a wide area of attachment what do they do. And they indeed hold the meniscus to the tibia so they support the position of the meniscus. You can imagine that there were a root ligament tear menisco displacement often is seen. Right, and we look for that. All right, because there may be menisco extrusion that is dramatic when you're dealing with root ligament tears. A few years ago, one of our visiting scholars from Korea did some beautiful anatomy of these these are some pictures taken from the work that he did to show you that the three other menisco roots just a couple words about them. The anterior root ligament of the medial meniscus typically attaches to the sloping anterior portion of the medial tibial plateau. The anterior root ligament of the lateral meniscus is intimate with the footprint of the anterior cruciate ligament, and maybe difficult sometimes to separate from it. And the attachments of the post the posterior ligament of the lateral meniscus are complex. That root ligament may attach both to the lateral and medial tubicles of the intercontinental eminence of the tibia, but we're not going to spend time looking at those. What we're going to look at is the posterior root ligament of the medial meniscus. This is intimate with the posterior cruciate ligament. As you can see, this is in the sagittal plane. Here's the posterior cruciate ligament. And here is the posterior root ligament located just in front of the PCL here are the specimen photographs showing you that. Here is an axial section. Here is the posterior cruciate ligament attaching to the tibia and here is the posterior root ligament of the medial meniscus intimate and slightly entered to the posterior cruciate ligament. And here in the coronal plane, this is the more posterior section. This is slightly more anteriorly. Here is the attachment of footprint of the posterior cruciate here is the beginning of the attachment of the posterior root ligament. And on the next most anterior section there is the full attachment of the posterior root ligament. So it is intimate with the PCL. This is what a tear, a full thickness tear of the posterior root ligament of the medial meniscus looks like. It ends abruptly. There is a gap much like the radial tear that I showed you earlier in this lecture. Now there is a classification system while by La Prade and by the way, but those of you who like to read the literature whenever you see La Prade, read the article because his articles are terrific. A lot of them have to do with anatomy. He has classified certain root ligament failure patterns. And here I'm showing you one of his classifications. They're five types. I'm not going to go into detail about them. But the one that I see most commonly is the type two, a complete or near complete pair of the posterior root ligament of the medial meniscus. And it is further divided into A, B, and C, depending upon how far that particular tear is away from the footprint of the root ligament. So just to give you some examples of it. Here are to a to be and to see cases. So this one is a rate is a failure pattern or radial tear close to the root ligament. And as we get further way to be and to see the gap becomes more prominent. And I want to call your attention, the further you get away from the footprint of the root ligament, the smoother is the end of the posterior horn of the medial meniscus. When the root ligament is involved itself you have a shaggy or regular end. So those are some patterns that we may see. The prequel to a posterior root ligament problem may be Maro edema. Here I show you on the left the prequel in the form of subtle edema. Four months later, this is a root ligament hair or evolution almost complete with a gap that has developed. So when you see cis or edema beneath the attachment side of that posterior root ligament, please pay attention. Here's another example. This is a root ligament evolution you can see there's a shaggy portion of the root ligament attached to the posterior horn. The gap this is the most important half image remember we talked about there's the gap. So seeing that you should not be surprised and when you look at the body of the media meniscus there are a number of findings that you will see the meniscus is extruded. The medial collateral ligament is complex is bowed. There is peri ligament is edema around those ligaments. There's often a demon like changes in the medial tibial plateau or medial femoral condyle. And for those of you who are sharp eye you will see the beginning of a small insufficiency fracture right there in the medial tibial plateau. We now know that tears of the root ligament posterior root ligament and other root ligaments can be associated with insufficiency fractures. Here's an example of a posterior root ligament evolution full thickness I think or complete. And here is the insufficiency fracture. It's an altered signal merging with the sub poundal bone plate here by the way I think this will work as the arthroscopy picture showing you the loosening. So insufficiency fractures are seen with root ligament tears as well as radial tears in this particular location. And what we used to call some which we thought was osteonecrosis something like this, we now recognize, not as necrosis but initial insufficiency fractures is another example. Plastic song. Right, what we used to call osteonecrosis of the femoral condyle, but this is an insufficiency fracture that has led to collapse of the sub condyle bone plate. Earlier we can see the posterior root ligament evolution with peripheral extrusion of the meniscus. Now the last five minutes or so a couple other associations, the meniscal ossicle. For many years it was felt only to be a normal finding was seen in large domestic cats such as lions and tigers, and typically was in the anterior horn of the media meniscus shown here. Unfortunately, you can't get much of a history from a tiger to know whether or not there had been an injury, but we thought seeing it in animals. It was developmental in humans. It may be developmental in humans typically circular or triangular, typically posterior horn of the media meniscus within that part. All right. But it also may be associated with root ligament problems with two possibilities, an evolution of the root ligament as shown in this case, or a soft tissue evolution with later secondary heterotopic ossification. So if you see these ossicles before you call it a normal variant, check the posterior root ligament. And the other finding was the meniscal clouds. If you look at our literature or the arthroscopy literature is considered a normal finding more commonly seen in the media meniscus than the lateral meniscus. It's an undulation of the inner portion. There's that undulation here. But my advice to you is whenever you see it, just go back and check to see if there's a problem here. Here's a posterior root ligament evolution. This posterior horn has moved forward. This is laxity now a pathologic flounce within that particular meniscus. And then finally, the postural lateral corner. There are a lot of structures that attach to the posterior horn. Among those structures, something called the fascicles or popliteal menisco ligaments. There are three of them, although some of us only have two. If you look at sagittal sections starting laterally and progressing medially. Here is the intro in fear popliteal menisco ligament. Here is the intro in fear and postural superior. This is known as the popliteus hiatus the tendon located there. And then here again we can see those two. More centrally we may get a postural in fear popliteal menisco ligament. So these are important attachments of the posterior horn to the capsule around the popliteus tendon is passing through the joint. Problems with these fascicles can be developmental, or they can be traumatic trauma trauma may be a single episode of an injury or repetitive stress here's an example of disruption of the intro in fear of fascicle. And you can see the elevation of the posterior horn. This is an interesting case, a patient who had intermittent locking. At the time the upper images were obtained the knee was not locked but these are disrupted popliteal menisco fascicles. Here one month earlier the images became available when the knee was locked and you can see that that posterior horn has now displaced anteriorly next to the anterior horn, owing to these problems. All right, creating the locking of the knee. So always look at this particular area. And the final concept in the last couple of slides. Look at all the structures that kind of attached to the posterior horn, not just these fascicles or ligaments, but the ligament of riceburg. And I'm showing you that an orange by the way, this is how you spell Humphrey no e Humphrey did not have an e in his name. That's another one of these menisco femoral ligaments. We have a tear of the anterior cruciate ligament. Any of these structures may tug away at the posterior horn. So what you may see these cases of ACL tears. This is a popliteal menisco ligament tear with some fibrosis. This is what is known as a riceburg rip, where the riceburg ligament has created a tear in the posterior horn of the lateral nexus. Again, in a person with a tear of the anterior cruciate ligament. Even in my allotted period of time or the two particular points I wanted to do I've reviewed menisco structure emphasize the collagen shown shown you the three classic patterns of menisco failure based on an understanding of its structure function and dysfunction of the meniscus of the knees. And I want to end with this slide, sent to me recently. This is just our conference if you're interested in upper extremity MR, I along with some terrific radiologist will be running a virtual conference both with lectures and cases. You're certainly welcome to join us. And with that in mind, I'm going to stop my share. And open up I guess for any questions. Thank you so much for sharing your lecture Dr. Resnick at this time we're going to open the floor for any questions. And remember to use that Q&A feature to submit a question and we'll we'll try to get to as many before Dr. Resnick has to go. Dr. Resnick, are there any nerve fibers in the meniscus is menisco failure itself the cause of pain. There are nerve fibers into meniscus and indeed menisco failure can cause pain. So what are the types of tears that can cause pain. That's been written about in the literature. Unstable tears are perhaps the most important one unstable tears are long longitudinal vertical tears. They are multi directional tears that's another one. And remember when you see a gap at the site of failure those are the causes of pain associated with menisco pairs. Can you please address articular cartilage imaging. Are you using any cartilage mapping or ultra short TE imaging. As you know, I have some incredible associates here at UCSD one of which is Christine Chung who is a someone who has written extensively on ultra short TE sequences, not just for articular cartilage, but for other things as well. We use them for research purposes it's not part of our standard. We use the MR assessment of articular cartilage. We use some gradient echo imaging for some of that. But the images with ultra short TE sequences, looking at articular cartilage or model this. And so, if you have that ability it might be something that you might want to consider. Is imaging an injury of riskberg image, similar to longitudinal vertical tear. And certainly the riceberg is a longitudinal vertical tear at the periphery you have to be a little bit careful about that because there is normally an area of intermediate signal between the riceberg ligament and the posterior horn of the lateral meniscus. The area of intermediate signal proceeds more latterly on multiple images it's likely a menisco pair. And by the way, that ligament of Humphrey can do a very similar thing although less commonly we call that a Humphrey hitch is the name we have for that finding. What is the healing potential of a posterior root tear. I don't think they heal. They, in fact, a tear particularly one that is displaced is has the same significance probably of doing a partial or complete medial menisectomy. It is likely highly likely that the articular cartilage and that compartment will in fact become quite abnormal. When you have radial pairs of that posterior horn or root ligament problems. Every step that you take the meniscus extrudes, like a partial menisectomy every step. And indeed when you look at patients who have those types of failure, you often see a Dima and thickening of the meat, a Dima about and thickening of the medial supporting structures because it's an unstable me with every step, the meniscus extrudes presses against the medial supporting structures. So root ligament tears do not do well and often are repaired. How do we measure long radial tears. Well, if you know if you can see them well on sagittal images, and you know the spacing and thickness of those images you just do simple mathematics. You can figure out and the figure that's given in some articles is that if they get over nine or 10 millimeters they tend to be unstable and painful. What is surgery indicated in a meniscal tear. When is a curve conservative approach adopted. That's interesting my own personal story is. I had a meniscal tear I'd like to tell you I was rock climbing but I rolled over in bed. And I tore the enter a horn of my lateral meniscus and I went to the orthopedic surgeon and a very good one and examine my knee and he said you know you've got a tear. And I said, yeah, we don't need an MR I don't believe in MR. He said, well you're lucky, because we have an opening in our surgical suite two days from now I'm going to put you in I said, no, you know I've been reading the literature and some of these ones will heal on their own I'm going to put it off for a while and sure enough, that tear must have healed because my knee pain went away over a period of about three or four weeks. And one other point that, you know that red zone which is a peripheral phenomenon in the meniscus the one area that may not have a red zone is the posterior horn of the lateral meniscus where the puppeteers go through the joint. So that is why in the icicles classification that is separated out as a specific pattern of failure because there's no red zone there. So my feeling is that if you have a longitudinal vertical tear in the red zone of the meniscus, not displaced, you don't have me locking, I would probably elect for at least trying conservative therapy. I'm not sure every orthopedic surgeon would agree with that but that would be my philosophy based on my own personal experience. Does Discoid meniscus predispose meniscal dysfunction. You'll have to invite me back for a discussion about that because they are really remarkable. One of the problems with Discoid meniscus are problems in stability of the Discoid meniscus they develop menisco capsular problems. You can often see that as high signal, sometimes so high is called the Roman candle appearance. And what occurs in those cases, in some cases, intermittently is the meniscus displaces significantly. And so the knee locks. Alright, intermittent and the meniscus may flop back to its original position. So clearly Discoid meniscus I can cause menisco dysfunction symptoms certainly can arise. Awesome. How about one more and then we'll let you get back to rock climbing. If we see truncated meniscus, what should we infer or look for. Okay, so if you see member that's the gold standard abnormal morphology I believe that so strongly, not the signal, the morphology. In time, you know, hopefully you have a history there's been meniscal surgery. That's the first thing you have to consider. Alright, so what I do is I said at the very beginning of this lecture, I spend maybe 30 seconds or so scanning the and typically as I mentioned, you're going to see scarring in one pattern or another. It can be subtle sometimes in the antrometeal rather than the antrilateral. And one of our fellows wrote a beautiful article on that if anyone's interested you could Google my name all I did was proof read the article but if in that article we separated out right handed and left handed surgeons. We did find the preference for the antrometeal so efficient but maybe that's because of right handed surgeons who might put instruments through that the other aspect. But in any case that's the first thing I do. And if there is no history of surgery and I see no evidence of surgical scarring a truncated meniscus is an abnormal meniscus, and I will read a meniscal tear in almost all of those cases. Dr. Reismic, thank you so much for your lecture today we cannot wait for the upper extremities conference in September and to learn so much more from you. And thanks for everybody for participating in the new conference and asking such wonderful questions. You can access the recording of today's conference and all our previous new conferences by creating a free MRI online account. And be sure to join us next week on Thursday, August 31 at 12pm Eastern, we are doing a new conference from the archives where we will replay Dr. Suresh McCurgee's head in next space is made simple. You can register for this lecture at MRI online calm, follow us on social media for updates on future new conferences. Thanks again, thank you Dr. Resnick and everyone have a great day.