 This is the prone cadaver. This is the right side. I'm standing on the right side and the camera person is on the left side This is the posterior aspect of the propritial fossa. We have removed every structure This is the upturned reflected gastrocnemius, the medial head, the lateral head, upturned plantaris muscle And this is the soleus muscle. This muscle that we see here, this forms flow of the propritial fossa This is the propritius muscle and we can see it is taking insertion from the posterior aspect of the tibia Right tibia above the soleal line. This is the soleal line. This propritius muscle as it goes upwards and laterally I'm going to show from under the structures of the propritial fossa, namely the neurovascular structures We can see that the propritus muscle is moving upwards and laterally and here we can see it is dividing into two origins The main origin goes up like this under the fibular collateral ligament And my instrument has gone under the fibular collateral ligament and it gets the lateral femoral content This is the one which separates the fibular collateral ligament from the knee joint and the other origin is to this structure here This is the posterior part of the lateral meniscus in this portion It pierces through the posterior capsule of the knee which we have opened up It goes under the RQ8 propritial ligament on the posterior aspect of the knee which also we have opened out So therefore propritus muscle has got two origins one from the lateral femoral condyle under the fibular collateral ligament And the other is from inside the knee from the posterior aspect of the lateral meniscus The propritus muscle by virtue of its origin from inside the knee joint when it contracts It pulls the lateral meniscus away from between the femoral and the tibial condyles And therefore it reduces the chances of injury to the lateral meniscus The other origin of the propritus which runs under the fibular collateral ligament and gets attached to the femoral condyle It separates the fibular collateral ligament from the lateral meniscus and from the capsule of the knee joint And that is why the lateral meniscus is much less likely to be injured much less likely to be torn Arthroscopic view of a normal lateral meniscus and a torn lateral meniscus being repaired arthroscopically Incidentally we can also see that the fibular collateral ligament is a tight cord and it splits the insertion of the bicep femoris This is the outturned cut end of the bicep femoris to the head of the fibula And this is the other end of the bicep femoris and we can see that the fibular collateral ligament Splits the bicep femoris and gets attached to the head of the fibula The action of the propritus when the knee is extended not weight bearing Then it rotates the tibia five degrees medially When the leg is weight bearing then it rotates the femur five degrees laterally So therefore propritus muscle acts on rotation of the knee five degrees only when the knee is fully extended So that is one of the actions it also helps to lock and unlock the knee Now let's take a look at another structure we see this muscle here this is the semimembrinosus The semimembrinosus as it descends down it gets inserted onto the upper medial aspect of the tibia But we can see it is giving an expansion here this expansion is the one which reinforces the posterior capsule of the knee joint Number one number two we can see it gives an expansion which also reinforces the propritus fascia There also we can see and part of that we have split here Number three we can see it is giving some curved fibers which we have cut This is the oblique propritus ligament and under that was another series of ligament which is Also fused with the posterior capsule of the knee joint which we mentioned earlier All the arcuate propritus ligament under the arcuate propritus ligament The fibers of the propritus enter into the knee and get attached to the posterior aspect of the lateral meniscus This fibers that we see here this is the posterior menisco femoral ligament Which extends from the posterior aspect of the lateral meniscus and get attached to the medial femoral condy The posterior menisco femoral ligament is another one of the intraarticular ligaments Which holds the lateral meniscus in place The next structure that we see here is what we have lifted up here This is posterior cruciate ligament The posterior cruciate ligament has got two bands One band goes little medially and another band goes a little laterally the thinner band This whole thing is the posterior cruciate ligament The posterior cruciate ligament it takes attachment from the posterior aspect of the tibial condy And it goes up and gets attached to the lateral surface of the medial condy of the femur What is the action of the posterior cruciate ligament? When a person is walking downhill There is a tendency for the femur to slide forward on the tibia And therefore the posterior cruciate ligament prevents the forward sliding of the femur on the tibia Especially when walking downhill When the posterior cruciate ligament is toned We can elicit it by means of what is known as the posterior drawer sign Where the patient is sitting with the knee partially flexed If we can push the tibia backwards If we can push the leg back on the femur That is known as posterior drawer sign And it will be associated with pain That is indicative of posterior cruciate ligament death In some dissections we may be able to see a little bit of the anterior cruciate ligament here But in this case we cannot see it very clearly The next structure which I would like to draw your attention to And it's rather unique It's not very common is If you listen to me closely here We can hear the bony sound My instrument is hitting against a bony structure Under the origin of the lateral head of the gastrocnemius And we can see I have removed some of the fibers of the gastrocnemius here To show you that we can feel it also very clearly here This is sesameid bone within the lateral head of the gastrocnemius And that sesameid bone is referred to as fapella And we can see that this particular cadaver has a fapella These are two lateral x-rays to show you presence of the fapella Within the lateral head of the gastrocnemius There's a theory which states that the archaeopocrite ligament Is inversely proportional to the presence of the fapella Both are concerned with the posterior lateral stability of the knee joint These are some of the structures which I wanted to show you What do you need to the posterior aspect of the open out knee joint Thank you very much for watching Dr. Sanjasan You're 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