The glenohumeral Joint we'll talk about the structure and actions of this joint for structure we'll identify the components of the glenohumeral joint what makes up this joint what supports this joint and then as a result of the structure the actions we'll describe the movements of the glal humeral joint so Glen humeral joint is a sovial joint two bones come together wrapped in a sovial membrane bathe in sovial fluid the specific type of sovial joint is a ball and socket joint which means we have a ball that artic Cates with a socket that allows it to move in all sorts of directions in this fashion okay it is the most flexible or mov movable sovial joint has the greatest range of motion out of all the sovial joints is in fact all the joints in the body the components first there's a ball the ball is the head of the humorus the head of the humorus articulates with the socket which is the glenoid cavity forming the glenohumeral joint now the glenohumeral joint has this head and it's quite a large head as a matter of fact that articulates with this glenoid cavity but something that's unique about this joint is that only a third of the humoral head articulates with the glenoid cavity at a time what does this mean thumbs up with regards to flexibility giddy up it's got so much range of motion and very flexible flexion extension uh abduction adduction medial lateral rotation and circumduction but thumbs down on stability because of how um little the humeral head articulates with that glenoid cavity uh the is so so poorly stabilized that an analogy often used is that of a g te a golf te and a golf ball well the golf te is the glenoid cavity and the golf ball is the head of the humorus looking like this so thumbs up on flexibility because look at how much movement that getss but thumbs down on stability so this begs the question what structures are in place to help stabilize this glenohumeral joint well the following structures do that the glenoid labrum joint capsule and those four ligaments getting their names for the bones that they articulate with so let's go through each of these one by one first one the glenoid labrum to teach this one Let's do an analogy glenoid labrum is like a bowl and toilet PL so how's it like a bowl let's go back to this analogy where the golf ball sitting on the te if we take a look at whoa it can go this way or whoa you can go this way and because it's so unstable you can get the ball to fall right off so if we want to find a way to help make this so the ball the golf ball wouldn't come off so much what if we did this what if we put a bowl on top of that golf te so that when we put the golf ball inside that one look at that now when it moves around it's a little bit more stable and doesn't quite walk wobble back and forth as much well the glenoid laum is like a bowl again the analogy of the golf ball is the head of the humoris and the bull is that glenoid labrum and this glenoid laum is this uh fibrocartilagenous ring it's a ring of tissue made of fibro fibrous cartilage that then articulates with in this analogy the T which is the scapula that glenoid cavity so let's move that glenoid laum on which then knits itself into the surrounding periosteum and Bone and has attachment sites for a number of things for the glenohumeral ligaments as well as the long head of the biceps tendon we now add the head of the humoris on there and because this glenoid laum is just under a centimeter high or deep better way of putting it about 9 millimeters the glenoid laum increases the depth of the glenoid cavity by about 50% so there's one of its functions another thing is the glenoid laum like a toilet plunger so there's a plunger and we put a ball right there and if we put the ball in it can suction cup inside that one you put a little fluid especially like um gross fluid from the toilet it'll just stick right inside there well the glenoid labrum or this uh plunger has the suction effect the glenoid laum is like a toilet plunger when we put the two on there there's a suction effect that helps keep the head of the humorous adhered to this inside that uh socket joint okay and finally the glenoid laborum has an attachment of important tendon so there's our biceps tendon so the attachment of the biceps tendon that long head where we follow the long belly and that long head goes to the inner tubercular Groove and then inside the capsule wraps around and attaches to the super glenoid tubal but also to the top of the glenoid labrum so if we now have a view that we're looking smack on facing face to face nose to nose with the glenoid fossa there is the glenoid oid cavity or glenoid fossa and then that circular area in Orange that's the glenoid laum there is the biceps tendon it comes and attaches all to that upper part of the glenoid laum all right now the joint capsule this joint capsule that surrounds this entire glenohumeral joint before we talk about that let's take a l we detour to discuss sovial joint structure okay so joint capsule here we have a bone that meets another bone and where two bones meet it's called joint and what surrounds this uh what's found articulating between these two bones in Orange that's Highland cartilage or also known as articular cartilage and that's what enables like bumpers and cars so bone doesn't hit on bone just like car metal doesn't hit car metal bumpers hit each other that's articular cartilage now surrounding the shaft of the bone in purple is this dense collagenous connective tissue knitted into the compact bone by Sharpie fibers we call that periosteum per around osteum bone that periosteum better yet that dense irregular collagenous connective tissue continues over to attach to the periostium of the other bone and so this dense connected tissue that I have in green that connects the periosteum we call is the joint capsule and that joint capsule has lined internally by a sovial membrane that then produces sovial fluid that Li that uh bathe the inside of the joint this is what makes this joint so flexible and movable now that joint capsule is what pulls the glenohumeral joint together and it creates this instra capsular negative pressure that helps to keep that head of the humorous articulating inside uh that glenohumeral joint um now if we take the humoris and we just take periostium that then becomes the joint capsule that then becomes the periosteum there we have the joint capsule around around the glenohumeral joint with sovial fluid bathing the inside of this something I want you to notice along the bottom is here is this axillary fold now that axillary fold is there because Watch What Happens in this joint capsule we go to AB duct there's got to be some because this is so flexible there has to be some laxity in this joint capsule un able to do that movement however the problem is this increase risk of dislocation by having this axillary fold and being specifically this axillary fold increases the risk of dislocation inferiorly in an inferior Direction because it's not so tight all right some other structures is the coral humal ligament so on this picture there's the coracoid process of the scapula and there's the humoris and the ligament that connects the corid process to the humoris is appropriately called the coral humeral ligament and this what this helps to do is if you're then pulling yanking Force Through the humoris down that ligament helps helps to stabilize and keep the head of the humoris in the socket next is the coral chromal ligament attaching between the corid process and the AC chromian or chromal process going between the two and what this does is help is we've got the humoral head pushing up as if forcing the humoral head up towards the joint it helps then give stability to keep the head uh within the joint then we have this other one that courses between the corid process and the clavicle called the corco clavicular ligament and it helps anchor that clavicle inferiorly to ensure that it articulates at that joint and this joint is known as your acromial clavicular ligament and it helps to keep the clavical uh articulating with the scapula this is extremely important because it's one of the primary joints that articulates the Upper Limb to the axial skeleton all right so now that we've got this uh the structure of it let's talk about that there all these actions that the glenohumeral joint can do as shown by these illustration this glenohumeral joint will allow flexion and extension abduction and adduction and medial and lateral rotation so let's go through each of these in this lateral view of the right Upper Limb there is flexion is the arm goes forward and there's extension flexion extension great then abduction and adduction and so there is abduction moving the humorus away from the midline adduction moving the humoris towards the midline ab dection a dection and finally medial or internal rotation and lateral or external rotation so medial rotation is when the humorus goes medially lateral rotation it rotates laterally medial or internal rotation lateral or external rotation let's take a look at this from a anterior view there is medial rotation there's lateral rotation and let's add the same thing on medial rotation lateral rotation medial lateral so what we've now just covered is the structure of that glal humal joint as well as the what supports that joint as well as the actions accomplished by this glenohumeral joint