 Good day everybody. This is Dr. Sajja Sanyal, Professor, Department Chair. This is going to be the first demonstration of the knee joint. So what we have in front of us is the articulated skeleton of the knee seen from the anterior aspect. This is the left side and here the same thing we are seeing on the right side. Well first let's take a look at the bones which participate in the knee joint. The knee joint basically has got two components. One is the femoral articulation with the tibial. I'm showing the left side. This is called the femoral tibial articulation. That is one aspect of the knee joint. And the other aspect is the articulation of the fever with the patella which we can see on the right side. This is the femoral patella articulation. So these are the two components of the articulation. First let's take a look at the surfaces which participate. So again I've come to the left side. We can see this smooth surface here. This is the articular surface of the femoral condyle anteriorly which articulates with the patella. So this is the lateral femoral condyle. This is the b-tail femoral condyle. And this is the intercondyler fossa. And this is the one which fits in the patella here. And we can see that here. So that is the femoral patella component of the articulation. I'm going to subsequently remove the patella to show you the articular surfaces. With femoral condyle the inferior surface as you can see here is sitting on the flat plateau of the tibial condyle. And that's what makes the femoral tibial articulation. Having said that now let's take a look at the patella itself. So we are looking at the patella on the right side. And if you take a look at the patella inside too, you notice that the patella is roughly triangular in shape. It's got a superior base and an inferior apex. The lower portion is the apex. So this is the base of the patella. These are the sides of the patella on the either side. Attached to the superior aspect, the base of the patella, this red portion that you see here, that is where the quadriceps tendon is inserted. And over that there's a thin aponeurotic sheet. And then from the apex of the patella to the tibial tuberosity, we have a strong, tough ligament of patellae, which in effect is the continuation of the quadriceps tendon. Attached to the sides, we have the medial patellar red necrolum and the lateral patellar red necrolum. The medial patellar red necrolum is derived from aponeurotic expansion of the vastus medialis. And the lateral patellar red necrolum is aponeurotic expansion from the vastus lateralis. These are attached to the sides of the patella and they're attached to the sides of the tibial condyle. And these reinforce the anterior capsule of the knee joint. Having mentioned that, now I'm going to lift up this patella. And I'm going to turn it. So I have turned it now. When we turn it, we notice several articular faces. This is the larger lateral articular facet of the patella. And this is the smaller medial articular facet of the patella, which articulates respectively with this portion of the femoral condyle here, the medial one, and the larger lateral femoral condyle here. So therefore, if you were to take a very close look at the patella on the inside surface, we notice that there's a vertical ridge here, which separates the lateral from the medial. Each portion, the lateral and the medial has got a faint superior articular surface, a middle articular surface, and an inferior articular surface. The same thing can be seen on the medial side also, superior, middle and inferior. And on the extreme medial side, there's a small vertical ridge, which is the medial nonarticular part of the surface of the patella. Now, let's take a look at what happens when we flex the knee. So I'm going to show you on the left side because this is already articulated. When we flex the knee, you notice there's a condyle of the tumor, which is moving on the condyle of the tibia. At the same time, what happens to the patella? The patella is attached by the ligament of patella to the tibial tuberosity. So therefore, the patella moves down, or in effect, the patella surface of the femur moves away. And therefore, this portion gets exposed. And this is the portion, this surface, you can feel on yourself in your own knee, when your knee is fully flexed. And this is the portion which is occupied by the suprapatella bursa. So therefore, when we extend our knee, this patella then again comes back and sits here. And so therefore, at that point, the suprapatella bursa is likely to get compressed between the patella and the femur. And at the same time, the articular is genu muscle, pulls the suprapatella bursa away from so that it does not get compressed between the femur and the patella. This is an anterior posterior x-ray of the knee to show the location of the patella when the knee is extended. And this is an attribute of the knee to show the same situation. This is an athrogram of the knee by injecting carbon dioxide to show the location of the suprapatella bursa in relation to the patella. Now let's take a look at patella dislocation with respect to something called a Q angle. The Q angle basically is an angle between the vertical mid patella line or the line of gravity and the angle, the long axis of the femur. The long axis of the femur and the vertical mid patella line. That angle is called the Q angle. The word Q stands for quadriceps. I'm going to show the same thing here. The vertical mid patella line is running right through the middle of the patella to the tibial tuberosity. This is the same as the line of gravity, which goes through the head of the femur in a normal person. And the other line is the oblique line, which goes from the anterior superior iliac spine or the greater trochanter and goes across the length of the shaft of the femur. That is the oblique line. And so therefore the angle between these two lines is called the Q angle. Normally this Q angle is approximately nine degrees. Now we have two conditions. One of them is called genu velgum or nokni. The other is called genu varum or boleg. Now let's mimic these situations in this particular specimen here. We have mimicked the condition called genu velgum or nokni on the right side. You notice that the line of weight bearing now is going through the lateral femoral condyle and the lateral tibial condyle. So there is extensive pressure on the lateral condyles. That's the first aspect of nokni. So therefore there is a greater likelihood of degeneration of the lateral femoral condyles, both femur and tibia in nokni. The next thing we notice is that the mid patella line has shifted further medial, the mid patella vertical line, which goes from the middle of the patella to the tibial tuberosity. Long axis of the shaft of the femur is this one. So therefore now what has happened is the mid patella line is not the same as the line of gravity because the line of gravity has now shifted further laterally. Mid patella line has shifted medially and the long axis of the femur is still this. So therefore our definition was the q angle is the angle between the long axis of the shaft of the femur and the mid patella line. And since the mid patella line has moved medially, the q angle has become more. So therefore, when the q angle becomes more than 17 degrees, then it becomes significant genu valgum. In such a situation, there's a greater tendency for the patella to dislocate laterally by the stronger pull of the vastus lateralis. So this is what happens in genu valgum or nokni. Now we shall mimic genu varum on bow leg. Now we have mimicked genu varum or bow leg. I have removed the patella because the patella is standing to fall away. We notice now line of weight bearing has gone through the medial condyles, both the femur and the tibia. So therefore the line of weight bearing tends to cause degeneration of the medial femoral condyles more often. And therefore this portion gets degenerated. The second thing we notice is that line of weight bearing has gone medially. The mid patella line has shifted laterally. And this is the long axis of the femur. And again, as per our definition, the q angle is the angle between the long axis of the femur and the mid patella line. And because the mid patella line has shifted laterally, the q angle has become less than 90 degrees. So therefore, this is genu varum. And in this case, there is greater tendency of wear and tear of the medial condyles. So these are the points which I wanted to highlight to you about the articulation of the femoral patella, the dislocation of the patella, genu varum, genu welgum, and the q angle. Thank you very much for watching. Dr. Sanjay Sanyal signing out. Please like and subscribe to this channel. If you have any questions or comments, please put them in the comment section below. Have a nice day.