Since I wrote an article last month called 6 Ways to Improve Thoracic Mobility, I thought it would make sense to (finally) follow-up with a post on the anatomy of some of the structures involved in the exercises I described. Today’s blog will be the beginning of a short series on shoulder anatomy. I’m going to focus on what I feel is important to know and I promise I’ll keep things relatively basic so you don’t nod off and fall asleep on your keyboard!
The anatomy of the shoulder is divided into two distinct parts: the shoulder girdle and the shoulder joint. I’d like to start off this series by talking about the bones and the joints of the shoulder girdle.The two bones that make up the shoulder girdle are the clavicle and the scapula.
Above is an image of the right clavicle as viewed from the top. The right or lateral end of the clavicle is usually referred to as the acromial end, and the left or medial end is called the sternal end. These two anatomical locations will come into play later when I discuss the joints of the shoulder girdle. The shaft of bone between the acromial and sternal ends is simply known as the body of the clavicle.
This is an excellent picture of the scapula as viewed from the front (anterior), the side (lateral), and the back (posterior), respectively. Important landmarks to note are the coracoid process, acromion process, glenoid fossa (or glenoid cavity), lateral and medial border, superior and inferior angle (simply the top and bottom “point” of the scapula), and the spine of the scapula.
That wasn’t too bad, right? Now on to the joints of the shoulder girdle…
Technically, there are three joints formed by bones of the shoulder girdle: the sternoclavicular (SC) joint, the acromioclavicular (AC) joint, and the scapulothoracic joint. You’ll most often hear about the SC joint and the AC joint, but we’ll briefly discuss all three.
Sternoclavicular (SC) Joint
The SC joint is formed by the clavicle’s articulation with the manubrium of the sternum. It is a multiaxial joint, meaning that is has movement in three planes of motion. In shoulder girdle movements, the scapula moves on the rib cage primarily as a result of joint motion at the SC joint.
Acromioclavicular (AC) Joint
The scapulothoracic joint is an interesting joint because there is no articulation between the anterior scapula and the posterior rib cage. It is also not a true synovial joint because it lacks typical synovial features and its movement depends on the SC and AC joints. Between the scapula and the rib cage lie the serratus anterior and subscapularis muscles, which will be discussed in subsequent parts of my series on shoulder anatomy.
That sums up the main bone and joint features of the shoulder girdle. Check back soon when I’ll talk about the movements and muscles of the shoulder girdle. I know you can’t wait!