Anatomy of the Knee Joint - Basic Clinical Anatomy Revision - Dr Gill

[Music] [Music] hello and welcome back to the channel my name is dr james gill and join me for another clinical skills video today we're going to be talking about the knee which bob has kindly donated from next door um and in terms of the knee it's actually quite a fascinating joint and we're hoping that with the anatomy we're going to hopefully impart some of my love for this joint to yourselves at home now the knee is the largest joint in the body followed shortly afterwards by the hip and the ankle now whilst we're going to focus almost exclusively to the knee today it is important that we highlight the hip and the ankle with regard to knee pathologies because pain to the ankle or the hip for that matter can cause radiation so we may be getting pain at the knee that is not actually related to the knee joint itself but coming from the others now the knee provides you know a bread and butter work for orthopedic surgeons and that's largely because these joints can become damaged with age and can end up being replaced but as we'll talk about shortly the knee shouldn't wear over time just you know due to the passage of the ears but if we have imbalances to the knee we can get changes in the forces passing through it that can result in some problems so onto the knee this is probably my favorite anatomical joint and yes you can have such a thing i think there's something about the interplay between the bones and the ligaments and the tissues where we're going to get the bursa and the muscles interjecting into the bones here and just how everything functions together to give a smooth bio biomechanical you know joint it really is quite quite elegant you know even to the structures inside the joint the menisci and the internal ligaments allowing you know small degrees of movement to allow that fluidity of movement i think it's absolutely fascinating and with regard to that we're going to start off with the very basics the bones of the knee now there are three bones that make up the knee we've got the femur we've got the tibia and we've got inside the knee the patella now it's very important we highlight the fibula that we can see on the side of the um the leg laterally is not part of the knee it has a small function in terms of the rolls of some of the ligament attachments but it should not be considered to be part of the knee there are only three bones in that joint so before we go any further i just want to cover a little bit of vocabulary when we're talking about the knee and this is a right sided knee we need to have two words in our mind and that being medial so the inside of the knee and lateral that being the outside of the knee and an easy way to tell that when you're looking at patient is whilst we've said the fibula is not part of the knee joint it's a really useful landmark because the fibula is on the lateral side of the knee so with that in mind let's have a walk around the knee so when it comes to looking at the knee we've got the femur which is the largest bone in the body we're going to ignore the distal section for the moment and just focus on the proximal where we're dealing with the knee so if we remove the patella for a second we can see that there are these large swellings at the base of the femur on its distal aspect and this is where we've got the high line or articular cartilage covering two rounded protuberances and these are the femoral condyles now if i move that round to here we can sort of see this round smoothness here and that relates to the name of these condyles so condyle comes from the latin for knuckle and i think we can just about see where they're getting that from we've also got the patella in the patellar tendon as the second bone of the knee and below that we've got the tibia onto which everything is going to articulate so staying with the latin for a moment we've also got two enlarged areas above the condyles now we can see how these are named these are named the epicondyles because epi from the latin above and condyle as we've seen is this knuckle-shaped protuberance so it makes sense that these further swellings are the epicondyles as these regions are above the condyles now when it comes to the condyles they are so very enlarged because the forces that pass through our knees they need to be able to take the huge weight of the body exacerbated by the impact forces when we're walking and when we're running by having this significant girth to the bones here it allows them to have a large area for cartilage and shock absorbers for the menisci to enable smooth movement of the knee so we don't get any damage over the lifetime of the joint so when it comes to movements of the knee we've got flexion where we pull take the knee out of alignment we've got extension where it's brought into and perhaps even over a extension we're also going to have a small degree of rotation as the knee can slip across the meniscal coverings of the condylar surfaces and that's a crucial that movement is rotationally is very very important to making sure that we're optimizing our movement and keeping everything safe within the knee now whilst we say that um the knee and the hip are the bread and butter of the orthopedic awards it's important that we highlight that whilst we can replace the knee it's never going to be as good as the one you have and one of the crucial things that we lack in terms of artificial joints is this high line or condylar cartilage this cartilage again allows for the smooth movement of the knee but with all of our technology we haven't managed to create something that has such a low friction coefficient which is why artificial joints tend to have a limited lifespan they will wear out over time now at this point it's very important that i highlight that your knee should not wear out there are people who will unfortunately have pathology of the knee that will mean there is a disruption to the forces going through them and that is going to result in problems with the knee but as long as you use your knees as its evolved as it's designed it should easily last you a lifetime i mean look at it i mean it's designed for running on as we said we've got the epicondyles where the ligaments are attaching we've got this huge expanse of cartilage over the femoral and tibial condyles and between we've got this wedge of meniscus that allows to work as both shock absorber and helps us to move the knee in a rotational component ensuring that we can absorb and also um be more efficient in our standing but once we've got all this shock absorber present for the knee in the in the anatomical position as it were look at the patella and around it yes we've got some bursa that fill in these holes here but the knee is not designed for you to be spending years and years kneeling on pressing down over you know this is going to cause damage and wear and tear over time because it's not how the knee has evolved to function and we see that with people we rarely get wear and tear from straightforward use of the knee if there is any problems it's normally related to biomechanics where something like the patella is pulling off ever so slightly to the side it's not because you know we're over using the knee it's the biomechanics have changed things so for example if we've got damage to the meniscus that's going to mean our shock absorber is less effective and we get more friction here going back to the point about kneeling down you know if we use the knee in a way it's not evolved to handle we are going to get unexpected wear we are going to get unexpected damage over time so the patella is moving in the space between the femoral condyles in the trochlear groove here we can see that nice smooth movement here but if you're kneeling down on the patella over time that can cause wear and tear to this cartilage and similarly cause problems in that groove so that you get sticking and discomfort here increasing pain around this area and increasing the likelihood of wear and tear and osteoarthritis and we often see that in people who've been kneeling down in their careers rubbing the patella against the femoral condyles here and this is how we result in wear and tear of the knee not from overuse of the knee but for inappropriate use and the vast majority of early knee and joint pain is often biomechanics it's a problem with know the ligament it's a problem with the menisci it's a problem with the muscles and often brief you know assistance from the physiotherapist can often put you back um well in alignment and meaning that you're going to have good distribution of forces and that should remove the pain there it's only over the long term if these abnormal forces haven't been adjusted that we will then get that wear and tear just to reiterate on that your knee wants to be used the high line cartilage that we have here wants to be compressed it wants to be filled and surrounded by the synovial fluid walking exercise jogging even is good for your knee it's good for the cartilage whereas being inactive sitting down all day not exercising not getting the movement and the compression of this cartilage is going to cause it to not wear out but it certainly won't be as healthy as it is in a nice mobile used joint again i go back to the fact that it's when it's inappropriately used such as long-term kneeling that's where we get our problems so in terms of there not being any shock absorbers and things over the patella let's actually just have a look at the patella for a second so in terms of patella it's what's referred to as a sesamoid bone so a bone that is held entirely within a tendon and in terms of the front we can see some interesting things about the patella so a tendon connects muscles to bone so very much coming from the quadriceps to the patella we've got the patellar tendon now a ligament connects bone to bone so technically with the patella being a sesamoid bone from the patella to the tibural tuberosity is technically the patellar tendon however if you look at this ligament histologically you'll see it contains the same tissue fibers and structures as we find in a tendon so we would do describe the whole piece here as the patellar tendon but it's not incorrect to describe this part as the patellar ligament but i think that's more of a bizarre facet of anatomical nomenclature rather than true biology and the purpose of the patella here is to stop wear and tear at the patella tendon so we've got a huge amount of force exerted from the quads in order to straighten the knee so that force has to come down the patellar tendon here and if this cartilage covered bone the patella wasn't here then that would be putting a lot of strain on the patella giving a much greater probability of that patellar rupturing and as soon as that ruptures as you can see here the knee cannot extend which is why when we're assessing the knee we'll get the patient to hold their knee in extension because we know that the patella is intact but to reiterate that as soon as it goes the knee will lose our extension and we can see that sometimes when somebody goes to the gym they're putting extreme forces through the quadriceps tendon through the patella and into the tibial tuberosity and thus we can get an avulsion at the tibial tuberosity where it rips off we can get rips to the quadriceps muscle meaning the tendon comes off at the top and we can also get damage to the patellar tendon again where that can rip all of which can result in the loss of that extension and often quite dramatically so in those situations so having talked about the femur and the patella we probably need to come down to talk about the tibia as well in terms of the tibial plateau we've got this large flat area of bone where the tibia is flowing out proximally with a protruderance at the front again this area is the tibial condyles but i don't know about you but it doesn't half look like knuckles as much as the femoral condyles do on the front we've got the tibural tuberosity onto where the patella will insert and we do have a point of articulation with the fibular head but we are highlighting once again the fibula is not part of the knee joint so if we pull the femur out of the way we can see how the tibia here is scoop shaped you know it's concave unlike the convexity of the femoral condyles and this means we've got a wonderful area for those femoral condyles to articulate held within these cups that are exacerbated structurally and physically by the menisci here on the front of the tibia below the condyles we've got the tibial tuberosity and this is the insertion for the patella so as we mentioned if there's a problem with the patella and we get a rupture we lose the ability to extend the tibia but we can also get damage here of the tibial tuberosity whether it's a straightforward blow or whether or not it's a more progressive issue that can a impact on the patellar tendon but also a packed impact on the ability to extend the knee so there's a condition that affects the tibial tuberosity here in called adolescence slatters we get inflammation at this point and microavulsions due to repeated traction as this as the patient is growing and in some patients that can be incredibly painful every time they straighten out the knee because all of the force is going through this inflamed sore and slightly damaged piece of bone and unfortunately the main treatment for that is going to be rest ice and compression there with that we tend to see it most commonly in patients that are very active in their adolescence but we can still see it in students and patients that are not particularly active so it's not absolute on that side but we do know it seems to be related to the forces passing through this insertion point so having covered the bone above and the bone below we probably need to finally get to that inside of the knee and this is where the meniscus sit so the menisci are two c-shaped areas of tissue and this is fibrocartilaginous tissue it's quite robust and it's got much more movement than the condylar cartilage of the femur and the tibia and as you can see here there's a slight out raised outer edge of both of these c's and that has the purpose of a working as a shock absorber and b helping to increase cupping at the tibial condyles meaning you've got increased stability of the knee and stability that's a crucial word for the knee because everything in the knee is working towards stability whether or not it's the massive quadriceps whether it's the ligaments to the side whether it's the shaping of the menisci or the ligaments within the knee it's all about promoting stability of this joint and that relates to what i said right at the beginning it's changes in the biomechanics changes in the throughput of forces through this joint problems with stability for example that will result in wear and tear over time if you've got good biomechanics good stability you're not going to get wear to your joint just by using it so crucially stability of the knee is very important hence the meniscus shape where we've got a much steeper curve on the outside compared to a thinner area on the middle this stability is aided as the menisci can move slightly within the joint as highlighted by the transverse ligament in fact this movement helps the health of the knee when you stand straight your knee immediately rotates ever so slightly rotating toward the midline and this allows you to ankle anchor your legs slightly more firmly on the tibial plateau and gives more stability and means you actually use less energy when you're standing but this movement isn't without cost we can get small tears that can mean the knee can lock onto the menisci if that tear caused it to fold over and jam so you'd need to take the patient to theater in order to trim off that tear and try and return the menisci to position so it's not allowing knocking but as we've said if we trim part of this menisci we are going to result in instability of the knee so again going to have increased risk of wear and tear over time now in terms of that movement on the front of in terms of that movement on the front of the menisci we've got a ligament that helps to anchor the front part of the niska and this is like a guide rope on a trampoline it does allow some stretch and a little bit of movement but mainly keeps the trampoline or the meniscus here in this case fixed in position which makes sense we want a little bit of movement when the forces come down ensuring we've got good support and good capturing of those forces but we don't want excess movement of the menisci because that's going to cause significant problems in terms of damage to the meniscus we tend to get that with a forced injury where the knee turns but the foot remains flexed and we can see here how that femoral condyle can munch on that menisci if we get an excess turning force so that's often seen if the leg is fixed in the ground and the upper body twists for example somebody who's playing football and the studs had them anchored at that time so we've said that the menisci helps stabilize the joint and the transverse ligament helps anchor the meniscus here but there's four other structures the ligaments around the knee that help to increase that stabilization of the joint along with the muscles as well we've got two on the outside the lateral and medial collateral now it's worthwhile highlighting at this point that the lateral collateral is a true ligament you can easily see the start of the finish and it's nice to find borders by comparison the medial collateral is a lot broader because it's less of a true anatomical ligament a more of a physiological ligament formed from the blending of the muscles on the leg so the lateral collateral is injured with a blow from the inside of the knee so for example the blow comes in and bends the knee out resulting in a tear here to this ligament the converse is true for the medial collateral the blow comes in from the lateral side the outside of the knee resulting in a huge stretch here where we're not wanting it resulting in its rupture now once these are gone again we're going to get much more movement than we'd expect which will allow degeneration of the joint so we want to try and keep these contained and intact well for our lifetime but they're not as important as the cruciate ligaments these are directly inside the knee and if you have damage with these well your knee will never be the same again so these are beautifully named ligaments the anterior cruciate ligament and the posterior cruciate ligament now these are so named because as we can see in here they cross over hence the latin cruciate and their names are easy the anterior ligament stops the knee moving anteriorly and the posterior ligament stops the knee moving posteriorly and similarly you know the the anatomy guys clearly name these things beautifully because the anterior ligament shows where we're anchoring into the tibia so the anterior cruciate ligament is going from the posterior of the femur into the anterior of the tibia and at the back the posterior cruciate ligament is going from the anterior of the knee into the posterior of the tibia now the anatomists who name these really had their thinking caps on when they came up with the knees these names and i do think there is a significant degree of elegance to it this way now the anterior cruciate ligament is one ligament in its own right whereas the posterior cruciate ligament has this second meniscal femoral component that acts as a sort of a bit of a backup coming from the menisci there so even if the true pcl goes you've hopefully got a degree of a backup there and i can't underline this enough how important the ligaments are to the stability of the joint and thus the protection of the joint if one of these goes even if the surgeons are able to repair it we need to make sure that we strenuously engage with physiotherapy to strengthen the other muscles around the joint in order to provide the maximum support that we can so we've talked over the femur we've talked over the tibia we've talked over the patella our sesamoid bone and covered the menisci within and the anterior and posterior cruciate ligaments as well as the lateral and medial collateral ligaments so that's a good overview of our knee hopefully this has been useful to yourselves we've only really talked about oscar slatters as a pathology here but certainly drop comments down below if you'd like us to delve a little bit deeper into some of the pathology other pathologies that we can get with the knee if you'd be able to like the video i'd be so grateful because it tells youtube we're here and if you found that these have been useful please consider subscribing and you'll get a notification for when we're doing the next video with that in mind take care look after yourselves and we'll see you in the next one cheerio [Music] you