in this video we're going to be examining the most complex joint of the body and that is the knee joint and what's really interesting about the knee joint it's actually three joints that are surrounded by a single joint cavity so the first joint is the femoro patellar joint which is where the end of the femur meets the patella so it's located roughly give me a second with the pen located roughly right over here and so this is a gliding motion so it's a plane joint where the patella can kind of move along the distal ends of the femoral bone the other two joints are sort of flanking this it is the lateral and medial tibiofemoral joints so it's kind of uh well in this particular perspective in this sagittal uh sagittal section it's sort of on one side and on the opposite side so this is where the femoral Condes are going to articulate with the lateral and medial minisi of the tibia so it's usually around this sort of GrooVe area on either side of the Condes and this particular joint functionally is a hinge joint now the menisa here the lateral meniscus and the medial meniscus there's a big problem with these menisa in that they are only attached at the terminal end so they can actually get torn fairly easily so we'll go into what sort of protects this what other structures protect it but let's go back to the Joint so functionally it's a hinge joint meaning it's capable of flexion and extension but when you have partial extension of this particular joint there is some capacity for rotation but this only happens when it's partly sort of excuse me partly flexed not partly extended um and that's due to the fact that even though functionally it's a hinge joint structurally it is more like a bondar joint now the reason why it can't rotate when you're fully extended or fully flexed is because of the ligaments so let's move on to other attributes of the knee joint so when we look at the Joint capsule right we had mentioned how there's three joints in this one joint capsule another very interesting Quirk is that the joint capsule does not or is not fully fully enclosed so it's actually missing on the anterior end so it's going to be um thinning and then by the time you reach the anterior end it's pretty much absent uh and so when you look at the sinovial cavity in the joint capsule there are these little blind alleys that end up with a number of Bersa so there are at least 12 Bersa that are found uh in the knee point so one that I want to draw your attention to is the subcutaneous prepatellar Bersa so usually when you get kind of hit on the knee any kind of physical trauma this is usually the Bersa that gets damaged and why you might feel a little bit of knee pain now when we look at the articular cartilage uh the articular cartilage is usually very thin on both ends of the femur as well as the tibia so at the end of the day what gives the knee joint a lot of structure are going to be the tendons so the capsule for example is going to be reinforced by the muscle tendons from the quadriceps and the semi membranas muscle uh and then we'll also look at how in the quadriceps that tendon will give rise to three broad ligaments so let's look at the quadricep muscle so the three broad tendons you have the tendons of the quadricep muscle will give rise to the patellar ligament it also gives rise to both the lateral as well as the medial patellar reticulum uh excuse me retic I'm even having difficulty pronouncing it uh retinaculum so other things to note when the physician is examining the uh patellar reflex usually what happens is the uh little Tool The Hammer is going to hit just below the patella it's going to hit the patellar ligament and this is going to cause the quadricep muscles to stretch and in response to that stretch the quadricep muscle will then contract which is why you kind of kick out an interesting little bit here is that the brain actually subdues this reflex you could actually grab your hands like this and pull um and that sort of action sort of overrides the inhibition so you might notice that you can kick out more um when you do that particular action so let's look at some of the other ligaments we're going to discuss both capsular as well as extra capsular ligaments and then dive into some of the intracapsular ligaments as well so the purpose of these capsular and extra capsular ligaments is for the most part to help prevent any kind of hyperextension of the knee as well as to prevent rotation of the knee so in this particular anterior view we see the fibular collateral ligament right over here and the tibial collateral ligament there so these are two of the extra capsul ligaments a third one the oblique poal ligament this would be found on the posterior side so if we switch back to this particular image here the oblique poal ligament is really just a continuation of the tendon of the semi membran Asis muscle so you can see here's the poal ligament and it's the continuation here's the tendon okay and this posterior view you can see the tibial as well as the fibular collateral ligament they're going to be on opposite side since we're uh looking at a posterior view so then our our last uh capsular ligament is going to be the arcuate poal ligament so again we're going to be seeing it on the posterior side right over here the arcuate poal ligament and so this is going to basically Arc in a superior direction from the head of the fibula over the potius uh muscle so here's the TOS muscle it's kind of cut in this particular image here but the arc is going to go sort of over that muscle and it's going to reinforce The Joint posteriorly so now let's examine the intracapsular ligaments so these intracapsular ligaments they're going to prevent the anterior posterior displacement of the knee so they're usually going to be very taut and they will cross over each other that's why we call them crui ligaments cuz to uh crushi is the phrase to mean to cross so we're going to name them based on the attachment site on the tibia not uh the attachment side on the femur so they are outside of the sinovial cavity but they are within the capsule itself so the anterior cruciat ligament is is going to attach to the anterior side of the tibia while the posterior cruciata ligament attaches to the posterior part of the tibia so here we have uh the posterior cruciata ligament uh just to show you on this anterior View and then the anterior cruciat ligament is right over here okay so if we examine this particular figure here uh we're not going to really see it because it's underlying all of this so the last thing we want to touch on um with regards to the cruciat ligaments the anterior cruciat ligaments oops are going to um they're going to be preventing the forward sliding of the femur relative to the uh tibia uh and it's going to prevent uh hyperextension so when the knee is uh somewhat flexed it's going to be fairly loose but when you extend the knee it's going to be relatively taut now for the posterior cruciat ligament it's going to uh basically prevent backward displacement so posterior back anterior forward right so prevent backward sliding um and um so it's going to be preventing backward sliding displacement of the tibia uh or in other words the forward sliding of the femur so again this is all relative to the tibia which is what the attachment site is named after so the last important elements of structure has to do with the bones themselves so when you look at the uh let's see a little bit which figure would be a better one to show you when we look at the Condes it's a little hard on some of these images but the Condes of the femur as well as the Condes on the tibia they act sort of like ball bearing so they they can fit and when there is extension of the knee they kind of lock into place with the ligaments becoming very very taut so the poal muscle also facilitates that through contraction to keep your leg uh extended so let's look lastly at at very various uh knee joint injuries so we can absorb a lot of vertical force uh with the knees because there's a lot of again vertical like so right because your mass is on it and fortunately because of that locking mechanism because of the condil however the knee is very susceptible to horizontal blows so recall we talked about how both the medial and the L minisi are just attached and and it's very easily seen on this particular image it's just attached at the termin so in the middle part there is no attachment s so it's very susceptible to tears so a lot of times with these horizontal blows uh especially the lateral ones uh they can impact the collateral ligaments the cruciat ligaments as well as the cartilage