 So, this is going to be a demonstration of the interior of the knee joint. This is a supine cadaver, this is the left leg, I am standing on the left side and the camera person is also on the left side. Now let's take a look at the interior of the femorotibial articulation or the knee joint proper. For that we are going to flex the open out knee and we can see the interior of the knee much more clearly. So, we have cut open the capsule as you can see here to see the structures in the front. Let's start off from the lateral aspect. We can see this muscle here, this is the bicep femoris and the bicep femoris gets inserted onto the head of the febola which is here. And we can see that the bicep femoris tendon is split by this strong stout ligament which I have lifted up here, this ligament. This is the febola or collateral ligament which extends from the lateral femoral epicondyle, it splits the bicep femoris tendon and it gets attached to the head of the febola. Several characteristics of the febola or collateral ligament of the knee joint. First of all it's a short stout cord like structure. Number two we can see since I can put my instrument here it is free from the lateral side of the capsule of the knee and it is also free from the lateral meniscus of the knee. And the reason why it is free is because from behind one of the tendons of the popliteus muscle passes through here and it separates the febola or collateral ligament from the knee joint. This is the febola or collateral ligament. Now let's take a look at the corresponding ligament on the medial side. Now the camera person has moved to the opposite side to the right side of the cadaver to show the medial side of the left knee. This is the tibial collateral ligament which I have picked up here. We notice that in contrast to the febola or collateral ligament the tibial collateral ligament is a flat bank. It extends from the medial epicondyle of the femur to the upper medial surface of the tibia. Between the tibial collateral ligament and the upper medial surface of the tibia there may be a person. The next thing we notice is that the tibial collateral ligament is situated just under the insertion of the pest and serenus. This is the sartorius. This is the gracilis. Further posteriorly we have the semitendinosus. So sartorius, gracilis, semitendinosus, these three triple insertions which constitute the pest and serenus are located just superficial to the tibial collateral ligament. And between these three tendons and the tibial collateral ligament there may be a person, which is referred to as the ancerine person. We can see that we can pick up the tibial collateral ligament only in the lower portion. We notice that in the upper part the tibial collateral ligament is densely adherent to the tibial part of the capsule of the knee joint and is also adherent to the medial meniscus. So this brings me to a very important clinical correlation. Tibial collateral ligament is much more frequently ruptured compared to the fibrillar collateral ligament. And when this is ruptured it can also produce a bucket handle tear of the medial meniscus because it is fused here. That's about the two collateral ligaments. Now we shall show the meniscus. For that again I am going to flex open the knee. Again we have flexed open the knee. So these are the two femoral condyles and these are the two tibial condyles. This is the tibial plateau and this in between portion is the intercondyler eminence. We see this filmy structure here. This is the intrapatellar fold. It's a fold of synobium and it's got two extensions which are known as the ailer folds. So let's keep that aside. This structure which I've lifted up here, this is the lateral meniscus. We noticed that the lateral meniscus as the term implies the peripheral portion is wide and the inner portion is narrow. So therefore in section it looks like a wedge. The peripheral portion is attached to the fibrous capsule and it is also attached to the margins of the lateral tibial condyle by means of this ligament part of which we have retained here. This is referred to as the coronary ligament which stretches from the margins of the lateral tibial condyle to the margin of the meniscus and that's what holds the meniscus in place. The lateral meniscus has got an anterior limb which we can see here which is attached to the anterior part of the tibial condyle and it's got a posterior limb. It is more shaped like a C and we noticed that the lateral meniscus is free from the fibular collateral ligament and my instrument is passing freely under the fibular collateral ligament. This brings a very important clinical correlation. The lateral meniscus is very infrequently ruptured compared to the medial meniscus. One reason is because it is free from the fibular collateral ligament and the second reason why it is very infrequently ruptured is because the posterior part of the lateral meniscus which is not visible in this dissection gives partial origin to some of the fibres of the paupitius muscle which is in the back of the knee and when the paupitius muscle contracts it moves the lateral meniscus out of the way and therefore injury to the lateral meniscus is much less common and when it does occur it's usually a marginal tear. This is an orthoscopic view of a normal lateral meniscus and a torn lateral meniscus being repaired. So that's about the lateral meniscus. Now let's take a look at this fibro structure here. This is the medial meniscus. We can see that the basic characteristics are same. It is wide at the periphery, narrowed in the center and the peripheral portion is attached to the margins of the medial tibial condyle by means of this ligament here which we have retained. This is the coronary ligament, the medial coronary ligament. It extends from the margins of the medial tibial condyle to the margins of the medial meniscus. This is the anterior limb of the medial meniscus and the posterior limb again is not visible here. The two anterior limbs are bridged over by this ligament structure that I've lifted up here. This is known as the transverse ligament of the knee which holds the two anterior ends of the menisci together. The medial meniscus in contrast to the lateral meniscus is more semi-circular in shape. That is one difference. The second difference is as we trace the medial meniscus posteriorly we notice that it is densely and firmly adherent to the tibial collateral ligament. And I have lifted up the tibial collateral ligament here. We can lift up the lower portion of the tibial collateral ligament and my instrument has gone in. But as I push my instrument up, we find that it cannot go any further up because it is densely adherent to the medial surface of the medial meniscus. So this again brings an important clinical correlation because of the medial meniscus attachment to the fibrous capsule and the tibial collateral ligament. The medial meniscus is torn much more frequently than the lateral meniscus. And it has a very unique type of tear where the peripheral portion remains attached to the capsule and the tibial collateral ligament and the inner portion gets separated. And that kind of tear is referred to as the bucket handle tear. Apart from that, the medial meniscus can also have a marginal tear. So therefore the medial meniscus is torn much more frequently than the lateral meniscus. These menisci, they act as a cushion between the femoral condyles and the tibial condyles. And they help to partially stabilize the knee. The next structure that we notice is this tough ligament that I have lifted up here with my instrument. This is the anterior cruciate ligament. The anterior cruciate ligament extends from the anterior part of the tibial condyles and it gets attached to the medial surface of the lateral condyle of the femur further posteriorly. When a person is walking uphill, there's a tendency for the femur to dislocate posteriorly on the tibial. So therefore, anterior cruciate ligament prevents posterior dislocation of the femur on the tibia. It also prevents hyperextension of the knee and it also helps to regulate the internal rotation of the knee. So that is the role of the anterior cruciate ligament. If the anterior cruciate ligament is torn, then we can elicit what is known as a drawer sign, whereby when the person is sitting with the knee partially flexed, we can pull the tibia forward against the femur and that is known as the anterior drawer sign associated with pain, which is an indication of anterior cruciate ligament dead. We cannot see the posterior cruciate ligament because in this dissection, it is located further posteriorly. That brings me to a few clinical correlations pertaining to the knee. I've already mentioned about the injury to the lateral meniscus, which can rarely produce marginal tear. Injury to the medial meniscus, which is more common, can produce bucket handle tear as well as marginal tear, which is much more frequent than the lateral meniscus tear. When there is pain on medial rotation of the tibia associated with booking open of the lateral part of the knee and pain on the medial side, that is indicative of medial meniscus tear. Contrary wise, when there is pain on lateral rotation of the tibia with pain on the lateral aspect of the knee and booking open of the medial side of the knee, that is indicative of lateral meniscus tear. Then there is something called the unhappy triad of knee injury, which happens in very severe contact sports. In such a situation, three structures are torn. One, anterior cruciate ligament. Two, the tibial collateral ligament. Three, the medial meniscus. So this is referred to as the unhappy triad of knee injury. It is a potentially career-changing injury, especially which happens in sportsmen. And all of these require arthroscopic repair. Nowadays, arthroscopic surgery is done very frequently for the knee. And last but not the least, as we can see this cadaver, there is partial degeneration of the highline cartilage on the femoral surface as well as on the tibial surface. So therefore, degenerative osteoarthritis of the knee is also very common because it's a weight-bearing joint. And therefore, knee replacement arthroplasty is also quite commonly performed in advanced age. So these are some of the structures that we can see the open knee from the anterior aspect, the femoral tibial articulation and the various ligaments that we can see here. Thank you very much for watching. Dr. Sanjay Sanyal signing out. Mr. Kendall Cumberbatch is the camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day.