Shoulder Anatomy, How It Is Made Affects How It Works
Shoulder and Shoulder Complex Anatomy
Anatomy, how the body is built, is a key to understanding the role of the shoulder in the golf swing. In this segment we are going to study the anatomy of the shoulder girdle and the whole shoulder complex. There are many important structures and substructures in this area. The humerus, clavicle, scapula, ribs, and rotator cuff bones and muscles as well as a multitude of other muscles, ligaments, tendons, and nerves comprise the entire shoulder girdle complex.
To look at the boney structures of the shoulder complex we will begin with the shoulder girdle. This is the foundation of the shoulder. It includes the collar bone or clavicle, which extends from the breast bone or sternum to the shoulder, the shoulder blade or scapula, which is a large, flat, triangular bone that forms the back part of the shoulder and sits on the back of the ribcage, and the humerus or the upper arm bone.
The shoulder bones are linked by a series of joints that help create stability or allow movement. The joint between the shoulder blade and ribs is the scapulo-thoracic joint. This joint is not a joint in a classical sense, like the knee or elbow, but it is nevertheless an articulation between bones. The collar bone attaches to the upper portion of the breast bone at one end and the flange on the scapula, which you can feel at the point of the shoulder called the acromion. If you have heard of someone who has a separated shoulder, they have injured the acromioclavicular joint. The shoulder blade is also the home for the shoulder socket. It has a shallow socket that is perpendicular to the body of the scapular. This is called the gleniod fossa. It is more like a saucer or plate than a cup. It has a cartilage called the glenoid labrum that runs around the circumference of the glenoid fossa. Its job is to deepen the socket. Finally we have the humerus. At the upper end of the humerus, in the shoulder region, is the humeral head, or the ball. This sits in the glenoid fossa, and it is this joint that is the true shoulder. Seem complicated? It is! But its design is ingenious, as it provides a stable base that allows the arm to work efficiently.
There are a few other structures that we need to look at. There are bursae (fluid filled sacs that cushion the movement of muscles and tendons over one another. There are also nerves and arteries that run between the acromion and the head of the humerus. When these get pinched we experience pain.
One of the most unique structures in the shoulder is the joint capsule. Not that it is unique at a basic structural level, but its anatomical design is unique. A joint capsule’s job is to hold the joint together and allow motion. In this case, because of the magnitude of motion in the shoulder, the capsule has a large redundant fold in it at the bottom of the shoulder joint. It is this fold that also creates problems like “frozen shoulder” when injured. We will study that more in a later installment in this series.
There are a variety of muscles in the shoulder region. There are the rotator cuff muscles which course from the body of the scapula to the humerus. The rotator cuff is a group of four muscles that are designed to stabilize the head of the humerus against the glenoid fossa and control rotation and stability of the glenohumeral joint. There are several muscles that attach the shoulder blade to the torso. On the back there are the trapezius, rhomboid, latissimus dorsi, and serratus anterior. On the front there are the pectoralis major and minor. There are also muscles that run from the scapula to the humerus. These include the biceps, triceps, deltoid, and the coracobrachialis.
Like the other areas we have studied thus far, this all sounds very complicated, but it is actually quite simple. There are pairs of muscles on opposite sides of a joint or bone. These muscles act in opposition to one another to create mobility and or stability of the area where the muscle resides. The stabilizers generally attach the shoulder blade and collar bone to the torso, and the movers generally run across the shoulder. The key to a good golf swing and a pain-free shoulder is to make sure the pairs of muscles are working in sync with one another, in the correct sequence, and balanced in their tension and strength. This is the realm of golf fitness and preventing golfing injuries.
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Here’s to your healthy shoulders and good golf.