 Good day everybody. Welcome to the section of the Perpetual Fossa and Dr. Sanjay Sanyal, Professor and Department Chair. So let's take a look at the boundaries of the Perpetual Fossa. We can see a diamond-shaped space here on the back of the knee. The cadaver is prone. This is the left leg. That's superior. This is inferior. This is medial. This is lateral. Let's take the boundaries. This is the supramedial boundary, the supramedial boundary. The supramedial boundary is composed of these two muscles here. This is the semi-tendinosis and under that this is the semi-membraneosis. Both are the hamstring muscles and they are both supplied by TPL division of the sciatic nerve. The supramedial boundary is formed by the bicep femoris, composed of a long head of biceps and a short head of biceps and they are the ones which form the supramedial boundary and the short head is supplied by the common femoral division and the long head is supplied by the TPL division. Coming to the infromedial and the infrolateral boundaries, the infromedial boundary is the medial head of the gastrocnemius and the infrolateral boundary is composed of the lateral head of the gastrocnemius and under that we have this muscle here which is called the plantaris muscle. So these two constitute the infrolateral boundary. So this is the diamond shape structure. So therefore the Perpetual Fossa which is at the back of the knee has got an apex above, an apex below and two angles on the sides. The roof of the Perpetual Fossa is composed of a superficial fascia which contains the posterior femoral cutaneous nerve which has been removed and it also contains under that a deep fascia which is the perpetual fascia. At margin of the perpetual fascia is visible here, the rest has been removed. This is part of the perpetual fascia. Similarly on this side also most of the perpetual fascia has been removed. This perpetual fascia is actually a deep fascia which is continuous with the chelatellae above and with the drool fascia below. Let's come now to the floor of the perpetual fascia. This is the floor of the perpetual fascia and you can see very clearly how deep it is. The floor of the perpetual fascia is composed of three structures going from above below. We have this portion here. This is the perpetual surface of the femur. Below that, this portion here is the posterior capsule of the knee joint and further below we have this muscle here. A little bit of that is visible here. This is the perpetual muscle. This forms a lower part of the floor and incidentally we can see some of the expansions of the semi-membranosus muscle which forms oblique perpetual ligament and also contributes to the perpetual fascia and we can see that here. So they all constitute the floor of the perpetual fascia. Now let's come to the contents of the perpetual fascia. Let me show you the orientation. Right on top of superficially we see this structure here. This is the tibial nerve. Nerve, just under that we have the vein and we have the artery. So a simple mnemonic is from superficial to deep and from lateral to medium. We have the nerve, vein, artery. From lateral to medium, nerve, vein, artery and from superficial to deep or from posterior to anterior, we have the nerve, vein, artery. Let's take them one by one. This was the sciatic nerve which came from the back of the thigh and it divided at the junction of the upper two-thirds of the lower one-third. Sometimes it divides it lower down into the larger division, the tibial component, the pre-axial component which is L5S123 and the post-axial component or the common fibular component which is L45S12. The tibial component runs vertically down from one apex of the perpetual fascia to the lower apex too. And this tibial nerve supplies all the muscles in the back of the thigh and the back of the knee, back of the leg and goes right under the sole of the foot. The common fibular runs obliquely, laterally and it is under cover of the biceps and as it comes laterally we can see it winds around the neck of the fibular. This is a very important place and this is the place where if there's a fibular fracture the common fibular nerve can be injured and the patient will have foot drop and after that it goes under the fibularis longest muscle where it divides into a superficial fibular nerve and a deep fibular nerve. This is the common fibular division. Okay the common fibular supplies the muscles of the anterior and lateral compartment and it further goes down to the foot but in the perpetual fascia it gives branch to the short end of the biceps. So this is an exception. All the other muscles are supplied by the tibial division the common fibular supplies the short end of the biceps. One more branch that we can see here this is this branch of the common fibular the lateral sural cutaneous nerve which is a cutaneous nerve which supplies the back of the legs. So that's one content. Now let's take a look at the next content. So let's start from the top. We can see an oval shaped opening here. This oval shaped opening is the adductor hiatus where my instrument has gone in. This adductor hiatus is the opening between the two insertions of the adductor magnus between the adductor component and the hamstring component of the adductor magnus and it is from here that the femoral artery and the femoral vein they pass through and they enter the popliteal fossa and here they change the name from femoral vessels to popliteal vessels. So now what we are seeing here is in the popliteal vein and the popliteal artery. Popliteal artery gives rise to five branches in the popliteal fossa superior inferior medial lateral genicular branches. Some of those branches are visible here I have written but some many of those branches had to be sacrificed. Additionally it gives numerous branches to the muscles and particular branches. As we trace the popliteal artery further down we find that the popliteal artery it disappears from the popliteal fossa by passing under this muscle. This is the soleus muscle and this portion of the soleus muscle that you see here this is known as the tendinous arch of soleus. It disappears under the tendinous arch of soleus and this is where it divides into a posterior tibial a larger division and an anterior tibial. So this is the course of the popliteal artery. The popliteal vein also follows a similar course and the tributaries of the popliteal vein match branches of the popliteal artery. Now let me tell you something very important and that is the clinical correlation. The popliteal vessels especially the popliteal artery can get entrapped in three locations. The first location that it can get entrapped is at the adductor hiatus. The second site of entrapment is if you note the popliteal artery is running very close to the origin of the medial head of the gastrocnemius and this is where it can get entrapped. In fact there's a very complex classification called the love and wheel-end classification which mentions six different types of popliteal artery entrapment by the medial head of the gastrocnemius and collectively they are referred to as PAES, popliteal artery entrapment syndrome. So this is the second place where the popliteal artery and sometimes the popliteal vein can get entrapped. And the third place where the popliteal artery can get entrapped is when it is passing under the tendinous arch of Solius. I want to show you a few other structures. Take a look at this structure. This is the short-settingous vein. We started from the lateral side of the foot and it traveled on the back of the leg and it pierced through the popliteal spacia and it opens into the popliteal vein and we can see. The clinical significance of the short-settingous vein is that the short-settingous vein is accompanied by a nerve here and that is called the sural nerve. We use this vein as a landmark to identify the sural nerve or nerve grafting like for example injury of the facial nerve and of course during clearance of the popliteal fossa we had to remove the fat and you can see the depth of the popliteal fossa is almost as deep as the length of a finger. So all this was filled with fat and it also contained a group of lymph nodes which are collectively referred to as the popliteal lymph nodes. So these are the important salient points about the popliteal fossa and its contents. Thank you very much for watching ladies and gentlemen. If you have any questions or comments put them in the comment section below. Dr. Sanjay Sanyal signing out. Have a nice day. Hey guys don't forget to like and subscribe.