Video Summary

We kick off the course with a brief introduction of what we will learn over the coming weeks.  Then we start with the fundamentals, the bones, joints and ligaments of the shoulder. 

I always like to keep Day 1 short!  It's to give you time to go over this material again.  As always the basic anatomy underpins much of what you will learn in this course.  So do take your time with it.      

Video Transcript

[0:17] Hi, I’m Dr Rob and today we’re going to cover the shoulder complex. This group of four interacting joints which help make the shoulder incredibly versatile. As always, I will cover the bones, the ligaments, as well as the muscles including those of the rotator cuff. We will look at ways in how to assess the shoulder both in a still or static position as well as during movement. What are the key things to look for that are right? And what are the key signs when things are going wrong? We will also look at the common conditions of the shoulder including osteoarthritis, rotator cuff tears, as well as joint instability. And lastly, we will think about ways in how to incorporate all this information into our practice and teaching of yoga. There will be a strong focus on specific movements for specific conditions. So with that all said and done, let’s begin.

BONES OF THE SHOULDER

[1:23] So let’s begin by looking at the bones which form the shoulder complex. There are four that we need to learn. So you’re looking at a right shoulder, and you’re looking at it from the front. The first bone is this one here. That’s your humerus or upper arm bone. Then we have the scapula here or your shoulder blade. And then this bone here is your collarbone or clavicle. The clavicle then joins on to a bone here, and that’s called the manubrium. That’s part of your chest or breast bone (sternum). 

[2:13] So those are the four main bones, let’s now look at some specific parts of each of those. So first of all, the humerus. If I drop the model away and I turn the bone to the front you can see that it’s got a round surface here or shape to it. This is called the humeral head. This forms part of one of the joints of the shoulder complex. When I turn the model to the side, this is the outer side, we’ve got this bump of bone here. That’s called the greater tuberosity. A tuberosity is a prominence or prominent part of a bone. And then more towards the front here we’ve got the lesser tuberosity. In between both of those is a groove called the bicipital groove and I’ll come back to that in great detail much later. And then lastly we have the shaft of the humerus that runs all the way down the arm to meet the elbow. So that’s the humerus.

[3:27] When we look at the scapula once more if I turn it to the side. We’ve got this part here which is called the glenoid cavity. This is where the humeral head sits into and forms one of the joints. If I turn it back to the front we’ve got this large surface here which is called the subscapular fossa. One of the important muscles of the shoulder attaches to that part. When we turn it back here you can see that we’ve got this lowest part and this highest part. This is called the inferior angle of the scapula. And this is the superior angle of the scapula. Through here you’ve got this very prominent part here which is called the spine of the scapula. Beneath that, we have another fossa called the infraspinous fossa. And above it the supraspinous fossa. So infra, inferior to the spine of the scapula, and supra, superior to the spine of the scapula. Then we have what we can describe as a medial border on the inside and a lateral border on the outside. 

[4:59] Then there are two more parts we need to look at. Both are called processes. One is the acromion process. This very flat bone on the very tip of the shoulder blade here. And the other is the coracoid process here. Next, we have the clavicle. This runs close to the acromion process and all the way through to meet the manubrium. This is primarily made up of a shaft, but we can also break that down into a proximal end and a distal end. So a proximal end here closer to the middle of the body, and a distal end closer to the outside of the body. The manubrium has two parts that we want to consider. One is the jugular notch here and the other is the sternal angle here. 

THE 4 JOINTS OF THE COMPLEX

[6:22] So those four bones meet together to create four interacting joints that comprise the shoulder complex. First of all, we have the glenohumeral joint. This is made up of the head of the humerus here and the glenoid cavity here. Sometimes that’s abbreviated to the GH joint. Then we have the scapulothoracic joint. This is made up of the scapula here and the ribcage (thoracic cage). That’s sometimes abbreviated to the ST joint. Coming up to the top we have the acromioclavicular joint. This is made up of the acromion process of the scapula and the distal end of the clavicle. That’s sometimes abbreviated to the AC joint. Then lastly we have the sternoclavicular joint made up of the manubrium and the proximal end of the clavicle. This is sometimes abbreviated to the SC joint. So those four interacting joints need to work in a smooth and coordinated way every time we move the shoulder. What we’re going to do next is look at each individual joint much more closely so we can deepen our understanding of them.

THE GLENOHUMERAL JOINT

[7:55] So the glenohumeral joint is described as a ball and socket joint. The head of the humerus being the ball and the glenoid cavity being the socket. Straight away you can see there is a bit of a mismatch between the two. The head of the humerus is very large and the glenoid cavity quite small. That means there’s not actually much boney stability to the joint. That’s great for allowing movement and makes the glenohumeral joint one of the most mobile joints in the body, but it’s not great for stability. It also makes the joint one of the most common to dislocate. Dislocation is when the bones separate and are no longer touching. So we need lots of other things to try and hold it in the right position and keep the joint aligned. One of those structures is the joint capsule. That surrounds the bones through here, so every synovial joint has a joint capsule, that’s made up of collagen. That joint capsule can be broken down into distinct parts or bands which we can then describe as ligaments. Now the capsule creates a sealed environment for the joint and within that sealed environment is a pressure, a negative pressure. We call it negative intraarticular pressure. This is a bit like a suction device you might use on your car windscreen or window at home. [sucking noise] You stick the device onto the window and then it’s held into the right position because a negative pressure is created. When you try and pull it off, it won’t move unless you use a greater force. So this is exactly what is happening within the joint as well. There’s a certain negative pressure which is keeping the joint together. That’s very useful. Then there are many muscles around the joint which actively contract to draw the two bones together. We’ll look at those in more detail later. So that’s the glenohumeral joint. A very versatile joint, but quite unstable joint.

THE SCAPULOTHORACIC JOINT

[10:15] The scapulothoracic joint or ST joint is formed by the scapula articulating with the rib cage. So this is the front of the scapula. These are the ribs, and then the scapula can just move around those ribs in different directions. It’s not a true joint. There is no bony connection between those ribs and the scapula, no articulating surfaces. There’s no articular cartilage or joint capsule. Everything is held in place via muscles and other connective tissues. So this makes the scapula very versatile in the way that it can move but slightly prone to instability and also faulty movement. And this can have a great impact on the health and function of the shoulder. There are many key muscles which attach from the scapula onto the humerus which are key for stability of the glenohumeral joint. The scapulothoracic joint is a really important joint to understand. Many shoulder issues stem from problems around here. Lastly, consider that every time we move the shoulder in different directions the scapular movement also requires movement of the acromioclavicular joint and the SC joint. And those joints we’re going to look at next.

THE ACROMIOCLAVICULAR JOINT

[11:50] The acromioclavicular joint or the AC joint is formed by the acromion process and the distal clavicle here. This is a synovial joint. So there’s a joint capsule, synovial membrane, synovial fluid within the joint. It’s described as a gliding or a plane type joint. So it can move in relatively small directions and a small degree of movement, but that movement is still essential for the function of the shoulder. If we think about the clavicle for a moment, this acts as a mechanical strut to position the entire shoulder away from the body and therefore makes it more versatile and more mobile. 

[12:35] Now, around the AC joint connecting to the clavicle and the acromion are various ligaments. Let’s now take a look at those. The AC joint has a number of ligaments supporting it. Four of which are found directly around the joint here. These are collectively termed the acromioclavicular joint ligaments but can be separated into four distinct bands or parts. There’s the superior, inferior, anterior, and posterior joint ligaments. Further along, the clavicle are the coracoclavicular ligaments here. This consists of the conoid ligament and the trapezoid ligament here. Now, all these ligaments help assure correct alignment and function of the AC joint, and they are particularly important as they have very little help in this task from nearby muscles. Now you don’t really need to remember these individual ligament names as very often they will all be spoken of collectively just as the AC joint ligaments. 

THE STERNOCLAVICULAR JOINT

[14:24] So the last joint of the shoulder complex is the SC joint or sternoclavicular joint formed by the proximal clavicle and the manubrium. The clavicle essentially sits just on a little part of the manubrium and creates what’s termed a saddle joint. So a bit like the saddle on the back of a horse. That’s the shape of it. It’s also classed as a synovial joint. So again, a joint capsule is around that and it’s stabilised by four key ligaments and a solitary muscle, the subclavius which attaches around through here. So there’s very little in the way of muscular stability to the SC joint as well as to the AC joint which can be sometimes a problem if we damage those ligaments and they don’t regain their original tension. It can mean that the joint is now unstable and can lead to certain issues which we’ll cover as we go through this module. Do lastly consider that this joint is incredibly mobile and it’s something we don’t always appreciate. Every time we move the scapula in different directions, see how the clavicle is pivoting around my finger. So a very mobile joint and movements are something that we’re going to explore in the next section.

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