 Good day everybody. This is Dr. Sanjay Sanyal, Professor Department Chair. This is the second demonstration of the knee joint. The structure which I focused in front of you, this is the right side tibia. So these are the two tibial condyles, medial and this is the lateral tibial condy. The surfaces are flat that they are referred to as the tibial plateau. Here in front of us, we can see the corresponding part of the femur. This is the right femur. So this is the posterior aspect. Therefore, this is the medial femoral condyle and this is the lateral femoral condyle. So this femoral condyle articulates with this tibial condyle and this lateral femoral condyle articulates with this tibial condyle. So this is what constitutes the femoral tibial joint. This is the intercondyler notch on the posterior aspect of the femur. This is the plate x-ray of the right knee to show the femoral tibial articulation. This is the knee joint proper. Let's focus on the tibial plateau. We can see this portion in the middle. This is called the intercondyler area. And we can see there are two elevations. One on this side, one on this side. These are respectively referred to as the medial and the lateral intercondyler eminence. For the most part, this intercondyler area is outside the sinomial membrane. Reflection of the sinomial membrane. Only a little portion anteriorly is within the sinomial membrane. The so-called ailer folds of the sinomial membrane. The rest are all outside the sinomial membrane. We shall focus on principally two intraarticular structures. Namely the meniscile and the cruciate ligaments. First, let's take a look at the meniscile. Meniscile are discs of fibrocartilage. They are located between the femoral condyle and the respective tibial condyle. So therefore, this is the location of the lateral meniscus and this is the location of the medial meniscus. The lateral meniscus is more narrow and C-shaped. Therefore, the anterior limb and the posterior limb are very close to each other. The medial meniscus is wider and more semi-noon are in shape. So therefore, anterior and posterior limbs are far apart. These meniscile, they act as shock absorbers and they also help to stabilize the knee joint which itself is by nature quite unstable. This is an arthroscopic view of the lateral meniscus between the lateral femoral and the lateral tibial condyle. Then we have the cruciate ligaments. Why are they called cruciate ligaments? Because panlegament is attached here in this region of the anterior intercondyler eminence. That's why it's called anterior cruciate ligament and there's another one which is attached here which is called the posterior cruciate ligament. And they go up, they cross each other and they get attached to certain specific parts of the femoral condyles which I shall mention later. And because they cross each other, they are referred to as cruciate ligaments. They are very strong stout ligaments and they hold the fever against the tibia and prevent it from sliding forwards or backwards. Now let's take a look at the exact locations where these structures are attached. So we have already mentioned that this is the location of the lateral meniscus and this is the location of the medial meniscus. So we shall follow a simple rule. M, A, L. This is where the anterior limb of the medial meniscus is attached. That's M. This is the location of the anterior cruciate ligament. L. This is the anterior limb of the lateral meniscus. M, A, L. Then we have L, M, P. L stands for the posterior limb of the lateral meniscus. M stands for the posterior limb of the medial meniscus. P stands for the posterior cruciate ligament. So this is how the structures are attached. Three in front anterior intercondylar area and three behind the posterior intercondylar area. Connecting the anterior limbs of both the meniscus, we have the transverse ligament of the knee. And connecting the posterior limb of the lateral meniscus to the fever, which is here, is the posterior meniscophemoral ligament. Additionally, the lateral meniscus gives attachment, partial attachment to some of the fibres of the podcast muscle. Therefore, there is a gap in the posterior capsule of the knee joint here. And from here, the perpendicular muscle gives attachment to the posterior limb of the lateral meniscus. Therefore, the lateral meniscus is more mobile. But we shall come to that just a little later. That brings me to the exact locations where the anterior and the posterior cruciate ligaments are attached. Anticruciate ligament, I told you, is attached here. It goes obliquely up. And it gets attached to the medial surface of the lateral condyle of the femur. This is the lateral condyle of the femur. And if you go to look at it from behind, you will see this is the medial surface and this is the lateral surface. So, therefore, the anticruciate ligament is attached to the medial surface of the lateral condyle of the femur. That is the location of the anterior cruciate ligament. Now, let's take a look at the posterior cruciate ligament. The posterior cruciate ligament takes origin from here, from the tibia. And it goes up and it gets attached to the lateral surface of the medial condyle of the femur. So, this is the medial condyle of the femur. And this is the lateral surface of the medial condyle of the femur. So, this is where it gets attached. So, therefore, anterior cruciate ligament gets attached to the medial surface of the lateral condyle of femur. The posterior cruciate ligament is attached to the lateral surface of the medial condyle of the femur. That's how the cruciate ligaments cross each other. This is a coronal MRI of the knee to show the attachments to the cruciate ligaments to the femur. It also shows the men's guide. That brings me to the function of the cruciate ligaments. The anterior cruciate ligament is useful for walking uphill. When we are walking uphill, there is a natural tendency for the femur to slide backwards on the tibia. And therefore, anterior cruciate ligaments prevents backward sliding of the femur on the tibia. Another function is it prevents hyperextension of the knee and also helps to limit rotation of the knee. What is the function of the posterior cruciate ligament? It is useful for walking downhill. When we are walking downhill, there is a tendency for the femur to slide forward on the tibia and that is prevented by the posterior cruciate ligament. This also prevents hyperflexion of the knee. When there is a tear of the anterior cruciate ligament, we have a test called the anterior drawer sign. The patient is sitting with the knee flexed and we try to pull the tibia forward or the leg forward. If you can pull the leg slightly forward, that is called the anterior drawer sign. That is indicative of anterior cruciate ligament tear because pulling the leg forward on the femur is equivalent to pushing the femur back on the tibia. This is an arthroscopic view of the interior of the knee joint to show an ACL tear which is being repaired with the graft. Similarly, we have a posterior drawer sign which is indicative of tear of the posterior cruciate ligament. Again, with the patient sitting, if we can push the leg backwards on the femur which is equivalent to pushing the femur forward on the tibia. That is called the posterior drawer sign positive and that is indicative of posterior cruciate ligament tear. That brings me to some of the injuries of the meniscus. The medial meniscus as I told you is wider and on the medial side it is firmly adherent to the capsule of the knee and to the tibial collateral ligament. Therefore, medial meniscus is 10 times more likely to tear than the lateral meniscus because medial meniscus is much less mobile. And the most common form of tear that we can get is at the junction of the peripheral margin with the central portion in this region and that is referred to as the bucket handle tear. Though we can also get marginal tear. Medial meniscus tear is indicative of a sign where we turn the leg medially and if it produces pain on the medial side of the knee associated with slight booking open of the knee on the lateral aspect that indicates medial meniscus tear. Lateral meniscus tear is much less likely. First of all because it is more mobile. Secondly, it is not attached to the femur collateral ligament. In fact, it is separated from the femur collateral ligament by the origin of the popliteus muscle and thirdly because part of the fibers of the popliteus muscle take origin from the lateral meniscus itself and during rotation of the knee it pulls the lateral meniscus away and therefore lateral meniscus tear is much less likely. However, it does tear rarely and that occurs in the margin. So therefore, marginal tear can occur. And the tear of the lateral meniscus is indicated by pain or lateral rotation of the leg when there will be pain on the lateral side of the knee associated with slight booking movement of the knee on the medial side. This is an arthroscopic view of the knee joint to show repair of the torn lateral meniscus. So that is about the tear of the medial and the lateral meniscus. We can have a combined injury that happens in extreme sports and that is called the unhappy triad of knee injury. What is this unhappy triad of knee injury? It is associated with the tear of the anterior cruciate ligament. So therefore, anterior draw sign will be positive tear of the tibial collateral ligament which extends from the medial femoral condyle to the medial surface of the tibial and tear of the medial meniscus which will be indicated by pain on medial rotation of the leg. Combination of anterior cruciate ligament tear, tibial collateral ligament tear and medial meniscus tear is referred to as the unhappy triad of knee injury. So these are some of the points which I want to mention to you about the intra-articular structures of the knee. We are showing the right knee. Thank you very much for watching. Dr. Sanjay Sanyar signing out. Please like and subscribe. If you have any questions or comments, please put them in the comment section below. Have a nice day.