welcome back to anatomy and physiology on catalyst University my name is Kevin toh cough please make sure to like this video and subscribe to my channel for future videos and notifications in this video we're gonna be discussing the anatomy of the sternoclavicular joint or s SI joint and before we get into all this anatomy here and the functions of it let's first define what the s SI joint is it's an articulation between the manubrium of the sternum and the sternal end of the clavicle so we can actually see both of the SC joints right here we'll dive into that in a minute recall that the clavicle if we were to look at the full extent of it which we will on the next slide we'll come back to this the clavicle has two ends has a sternal end over here which is more proximal where we could say it's more medial that articulates with the manubrium of the sternum and then it has a more distal or lateral end which is the acromial end which articulates with the acromion of the scapula and actually this joint right here is actually the acromioclavicular joint which will be the subject of the next video okay so two ends of the clavicle we're gonna be focusing here on the SC joint which is the sternal end of the clavicle but just to remember that it has two ends okay now here we see an anterior view of the sternum the manubrium so this is an anterior view that makes this over here the patient's left sternoclavicular joint and over here this is the patient's right sternoclavicular joint and before we really get into all this stuff over here let's actually get some landmarks so we know what we're looking at right here is the superior part of the sternum this is the sternums manubrium or a manubrium of the sternum down here is the just a part of the sternal body with a body of the sternum which is inferior to the manubrium notice here there's a joint that connects the manubrium to this to the body of the sternum that's called the sternal angle it has a couple other names you might see it's also called the angle of Louie and then it's also called the manubrium joint okay now on the manubrium we have a few other pieces here up here at the top we see this concavity right here this is called the jugular notch we'll come back to that in a few minutes we have a ligament that actually runs over the jugular notch over here we have a concave a that's on the right and the left side this is actually called the clavicular notch and based on its name this actually tells you that this is the notch where the clavicle articulates there's also an attachment site right here for the first rib notice the first rib articulates completely with the manubrium and then down here we have an articulation for the second rib or an attachment site for the second rib you should notice that the second rib actually articulates half with the inferior part of the manubrium and then half with the superior part of the sternal body so actually the articulation for the second rib spans both parts of the sternum here ok so here's the first rib you can see that the articulation with the manubrium is via costal cartilage that's going to be characteristic of ribs 1 through 7 so here's the first costal cartilage there's the costal cartilage of the rib 1 on the patient's left side and here's the left rib 1 and of course here's the two clavicles one on the patient's right here's the clavicle and the patient's left and you can see here the sternoclavicular joint now what they've done here on the patient's right side so this is the left side of the image is they've done a frontal section so you can see inside the joint capsule and what's notable about the sternoclavicular joint is actually that inside the joint capsule there is a layer of fibrocartilage let me actually zoom in so you can see that a little bit better so this is actually fibrocartilage right here this is called the articular disc of the sternoclavicular joint and this is very important because anatomically speaking the sternoclavicular joint is a saddle type joint saddle type joints really only permit movement in two planes and however the sternoclavicular joint allows movement in all three and that's because the articular disc actually transforms an anatomical saddle joint into a functional ball and socket so it's going to function similar to the shoulder joint or the hip joint a ball and socket and atomically it's not a ball in socket but functionally because of this articular disk it is what this articular disk also does is it creates two separate joint cavities or synovial cavities for the SC joint because it is a synovial joint we have here the cavity that's closest to the sternal end of the clavicle and we have another cavity that's closest to the clavicular notch of the manubrium okay so two joint cavities created by the articular disc but the main thing that's important about the disc is transforming it into a ball and socket joint which can allow movement in three planes and we'll see that on the next slide how that's important now over here on the patient's left or the right side of the image we can actually see the joint capsule the frontal section has not been taken here so this is the joint capsule between the clavicle and the manubrium of the sternum so the SC joint capsule and what we see here is that there's thickening of the joint capsule both anteriorly and then if we were to look on the other side posterior lis these thickening ''s are called the anterior and posterior sternoclavicular ligaments we can of course see the anterior sternoclavicular ligament here flipping this around we'd see the posterior sternoclavicular ligament there's another ligament over here which you can see connects the costal cartilage of rib one to the clavicle and this is called the cost of clavicular ligament okay these three ligaments collectively the anterior and posterior sternoclavicular ligaments and the cost of clavicular ligament they collectively stabilize the s SI joints they're the three main ligaments stabilizing the sternoclavicular joint now there's another ligament here that doesn't directly stabilize the SC joints but it does it does attach to them that is via the joint capsule it really just plays a role in connecting the two clavicles to one another and that's called the inter clavicular ligament we follow the incircle immaculate ligament from the patient's left side we can see that it originates here on the superior aspect of the clavicle it runs over the joint capsule and then traverses over the jugular notch of the manubrium and then it goes up the patient's right joint capsule and then hits the right this is the inter clavicular ligament and when we do a review of this in the future video will actually see another picture where we'll see another view of all these ligaments in terms of the blood supply and nerve supply to the sternoclavicular joint the blood supply is via the internal thoracic artery and the suprascapular artery on either side and the nerve supplies via branches of the suprascapular nerve and the nervous of Clavius remember that between the clavicle in the first rib there's a muscle here called the subclavius which plays a role in depressing the clavicle so there's a nerve to that called nerve to subclavius and there's a few branches that come off of that that'll actually serve the ipsilateral sternoclavicular joint okay so hopefully this makes sense to you now let's go look at the functionality of the sternoclavicular joint now anatomically speaking if we neglect that articular disc the type of joint and topically speaking is a saddle joint saddle drinks really should only a permit movement in two planes however because of the presence of that disc we have a functional ball in socket and you can see here that there's movements in all three planes and that's very important for the movement of the clavicle now it's important here is that more or less the s SI joint is fixed okay the movements occur about the axis or AXYZ at the sternoclavicular joint and that's because the manubrium doesn't move okay you can move your shoulder all you want put your finger or hand on you're maneuvering the maneuver Europe doesn't move so the s SI joint is fixed whereas if we look at the acromial end of the clavicle here we see it articulates with the scapula and this joint right here is actually the acromioclavicular joint which is the subject of the next video now what's important to know is that every single movement of the scapula right here is associated with a movement of the s SI joint okay so to understand this let's imagine scapular elevation this is the easiest one to understand this is basically where you shrug your shoulders up when you shrug your shoulders up the scapula elevates and moves up right now because the acromial end of the clavicle articulates and is connected with the scapula if the scapula moves up then the a crome end of the clavicle also moves up and that movement occurs about a fixed axis at the SC joint right here you can actually see the hinge right here that's supposed to show you where that movement occurs about whenever you're moving the acromial under the clavicle up during scapular elevation and the reverse is also true if you depress the scapula bring it back down well the acromial end of the clavicle still connected to it so the acromial end also depresses and you get a similar movement in the opposite direction about a fixed SC joint okay you can also do protraction and retraction of the SC joint so again if you protract the scapula that would be like if you're reaching forward to grab something far away from you on a table or you're doing a bench press your scapula is going to protract so it's gonna move forward and so you can imagine it moving away from the screen toward you that's protraction of the scapula well if you protract the scapula in that direction the acromial end of the clavicle is also gonna move in that direction this arrow right here it's gonna move toward you out of the screen and it's gonna occur about a movement again at a fixed SC joint in fact that movement is actually at this axis right here a vertical axis you can also retract the sternoclavicular joint if you retract the scapula so retracting the scapula would be like if you're doing rows in the gym so basically bring your elbows and put them as posterior as you can behind your trunk and if you do that you retract the scapula moves into the screen away from you so therefore the acromial end of the clavicle also moves away from you into the screen and again that occurs about a fixed SC joint really at this axis right here okay also notice you can do posterior and anterior rotation of the sternoclavicular joint so this is the rotational movement they haven't shown anterior rotation but you can rotate it okay about an axis that goes through the clavicle like this and then you can rotate it back to its original position for anterior rotation and you can see they're all three planes are accounted for which basically means that this has to be a functional ball and socket joint very important for function of the SC joint and also very important for movements of the scapula what we've seen here is that any movement of the scapula produces a corresponding movement of the SC joint so for example if you're doing shoulder abduction so basically in the gym you're using your deltoids doing shoulder raises okay that's producing shoulder abduction okay when you do shoulder abduction your scapula moves in fact your scapula will actually elevate and undergo upward rotation so because there's a movement of the scapula you'd also have a movement of the SC joint hey if you're doing a bench press or dumbbell flyes you would actually be protracting the scapula during the upward phase so if you're protracting the scapula and that's a movement of the scapula it would also produce a movement of the SC joint so the key is you can't have a movement of the scapula without a corresponding movement of the SC joints so they work in tandem completely okay so hopefully this gave you a good understanding of the sternoclavicular joint in the following video we're gonna start talking about the a chromeo clavicular joints so now we're shifting toward the distal end of the clavicle and we'll introduced even some more complexity here please make sure to LIKE this video and subscribe to my channel for future videos and notifications thank you