Glenohumeral Joint

00:01 So, now, let's move on to the glenohumeral joint or the shoulder joint as many of you will be familiar with.

00:07 So, the glenohumeral joint is really formed by a couple of key articular surfaces.

00:13 We have the head of the humerus, this nice smooth surface here.

00:17 And then, articulates with a similarly smooth surface which is the glenoid cavity.

00:22 Surrounding the glenoid cavity and helping the bony congruity so the head of the humerus to actually sit against this space, we have a layer of connective tissue called the glenoid labrum and that helps to increase the surface area of this space, even though, wanting to maintain mobility, it helps to have the head of the humerus sit firmly against the glenoid cavity, giving it some further substance.

00:48 So, here, we have the glenoid cavity in between the head of the humerus and the glenoid labrum which we can see there.

00:55 This is all surrounded by a joint capsule and this is quite a thin joint capsule, really allowing for great mobility of this joint.

01:04 We can see the joint capsule is running from the neck of the scapula, all the way to the anatomical neck.

01:09 And we can see actually that it's reinforced by a number of glenohumeral ligaments that really thicken this joint capsule.

01:17 We can see there's three of them, inferior, middle, and superior thickening of that joint capsule.

01:24 And then, we also have a coracohumeral ligament.

01:27 That's running from the coracoid process across to the humerus.

01:30 So, running over the top of that joint. We've mentioned the transverse humeral ligament before.

01:36 That's helping to form the intertubercular sulcus which has the long head of biceps tendon running up between it, between the two tubercles of the humerus. Here, we can see the coracoacromial arch.

01:49 Now, this is an important structure. Here, we can see the coracoid process.

01:53 Here, we can see the acromion and here, we have that coracoacromial ligament.

01:57 And that helps to prevent superior dislocation of the humerus within this joint.

02:04 The glenohumeral joint is a weak joint compared to the hip joint which we'll talk about later on.

02:12 It's really compromising its stability to increase the range of movement.

02:17 So it is often prone to dislocation. So, because of that, there are a number of important muscles and tendons which really help to hold the head of the humerus in that glenoid cavity.

02:28 One of them is the long head of biceps tendon which we can see here, biceps brachii tendon.

02:34 It's long head running over the superior aspect of the head of the humerus, over the glenohumeral joint, attaching to the supraglenoid tubercle.

02:43 We also have subscapularis muscle helping to hold the glenoid cavity together, holding the head of the humerus in the glenoid cavity.

02:51 And we also have a number of scapular humeral muscles in addition supporting this.

02:57 So, supraspinatus, infraspinatus, and teres minor.

03:01 These rotator cuff muscles helping to really hold the head of the humerus within that glenoid cavity.

03:08 We have a number of bursae, synovial sheaths that actually aid the movement of these tendons to help reduce friction as the shoulder joint is highly mobile, it's important that we have these bursae there to help prevent that friction.

03:23 So, we have the subtendonous bursa of the subscapularis, the subacromial bursa, the subdeltoid bursa, all of these bursae here, we can see the intertubercular tendon and its synovial sheath helping to reduce the friction that goes around this joint.

03:38 As it's highly mobile, there's lots of movement of these tendons running against that joint capsule and these help to reduce that friction.

03:46 If we have a look at the movement of the glenohumeral joint, here, we can see we've got adduction and abduction, so, the humerus being both close to the thoracic cage and moving away.

03:57 We can also see there's rotation, both internally and externally or lateral and medial rotation.

04:04 We can see the humerus rotating.

04:06 We can see that we have circumduction, so, the complete movement of the glenoid cavity.

04:12 Again, we can see high mobility here.

04:15 You can't do this with your thenar for example, within the hip joint.

04:19 So, complete circumduction of the humerus. And then, as you'd expect from previous lectures we've seen, you've got flexion and extension of the glenohumeral joint.

04:29 The blood supply to this joint is really important and it can see it's coming from a number of different branches.

04:35 We've mentioned these branches before but to recap, you can see them coming off of the axillary artery here.

04:41 We have the anterior and posterior circumflex arteries.

04:45 These are running around and forming an anastomosis around the surgical neck of the humerus.

04:50 And they give branches that go to the joint cavity.

04:53 As will branches of the suprascapular artery and the circumflex scapular artery.

04:58 Remember, these form an anastomosis on the posterior surface of the scapula and they've also given branches that go and supply the joint capsule around the head of the humerus and the scapular glenoid cavity.