Glenohumeral Joint – Joints of Upper Limb

00:01 So now, we’re going to look at the glenohumeral joints or the shoulder joints between the head of the humerus and the glenoid cavity or the glenoid fossa on the head of the scapula. And we can see on the screen, we’ve got numerous images which show different views of this joint. So here we can see a section through the joint. We can see we've got the head of the humerus here, and we’ve got the glenoid cavity. We can see the shallow glenoid cavity and the relatively large head of the humerus. Here, we can see a lateral view. We can see the glenoid cavity and how it’s deepened via this glenoid labrum. And then we can see some of the ligaments that are helping to support this joint. So if we look at the articulation, then as I mentioned, we have this large humeral head. But it’s running up against this shallow glenoid cavity. Now, although this allows increased range of movements, it means there’s reduced stability. So when we look at the hip joints in the lower limb lectures, you’ll see that the equivalent of the glenoid cavity, the acetabulum is very deep, and it actually holds the vast majority of the head of the femur. Here, we’ve only got a very shallow glenoid cavity for that large humeral head. The glenoid cavity has reinforced this deepened by this fibrocartilagenous glenoid labrum. We can see the glenoid labrum here. We can see it running all the way around the glenoid cavity. And this serves to deepen that recess which the head of the humerus sits. We can see we’ve got the glenoid labrum running around here, helping to deepen that cavity. The humeral head is held in the cavity, if you remember, by the tonic contraction of the rotator cuff muscles. This scapulohumeral muscle passing from the scapula to the humerus, the supraspinatus, infraspinatus, subscapularis, and teres minor muscles. The base old contraction, the tonic contraction of this muscle actually pulls the head against the glenoid cavity, and this actually helps to stabilize the joint. The fibrous capsule of the glenohumeral joint is relatively loose.

02:19 This allows the increased mobility. If it was tight, then you wouldn’t have as much mobility, and it’s running from the glenoid cavity to the anatomical neck of the humerus.

02:29 So we can see we’ve got the anatomical neck of the humerus here. Remember, it’s between the tubercles of the humerus and the head of the humerus, and it attaches here to the perimeter of the glenoid cavity.

02:48 Superiorly, the joint is actually reinforced because we have the tendon of long head of biceps. And here we can see the tendon of long head of biceps. Remember, it’s passing through the intertubercular sulcus, the intertubercular groove between the two tubercles.

03:07 It’s running up, over the head of the humerus to attach to the supraglenoid tubercle.

03:13 And this along with the acromion helps to reinforce the joints superiorly. Inferiorly, the joint is very loose, and there is no reinforcements inferiorly of the capsule. And if the humerus is to dislocate at the glenohumeral joint, it typically will be an inferior dislocation.

03:32 The head is then pulled forwards via the action of pectoralis major muscles. So let’s have a look at the ligaments to support it. Well, we have the glenohumeral ligaments. The glenohumeral ligaments, we can see here, are found anteriorly and they strengthen the joint anteriorly.

03:52 We can see we’ve got superior, a medium, and an inferior part of the glenohumeral ligament, and these are running here. Here, we can see the tendon of subscapularis passing to the lesser tubercle, one of the rotator cuff muscles, and that will be coming from the subscapular fossa. Here, we can see the anterior view of the joint. So we can see the coracoid process here as well. But here, we have the glenohumeral ligament, superior, medium, and inferior, we can see lying anteriorly to reinforce the joint. We also have the coracohumeral ligament.

04:30 The coracohumeral ligament passes from the coracoid process to the greater tubercle of the humerus. And this is a strong band. It strengthens the joint again superiorly.

04:44 So we can see the coracohumeral joints running across here to the coracoid process and it passes to the greater tubercle of the humerus. It strengthens it superiorly. We also have the transverse humeral ligament. And this bridges the intertubercular groove. It attaches to the greater and lesser tubercle. So we can see it running over here. And it creates that tunnel for the long head of biceps to pass through. We also have a complex arrangement that again is very strong and it prevents superior dislocation. And this is known as the coracoacromial arch. We have the coracoid process, we have the acromion, and we have the coracoacromial ligament. Remember, the coracoacromial ligament helping to augment supports the acromioclavicular joint. Well, it actually forms a roof over the superior aspect of the glenohumeral joint. And this serves to prevent superior dislocation.

05:54 Movements at the glenohumeral joints are flexion-extension, abduction, adduction, we’ve got rotation, and we’ve also got circumduction. And these movements cover a wide range and they’re possible due to the high number of muscles that enable these movements. And also the loose fibrous capsule and the arrangement of the head of the humerus onto the glenoid cavity, these allow a high range of movement.