The Enigma that is the Shoulder
By Dr. Robin Armstrong • August 22nd, 2012 • 11253 Views
The shoulder is one of the most misunderstood joints of the body. It can be susceptible to injury in yoga because we often demand a great deal of work from it that it is not designed to do. It has been a long time since we walked on all fours, but in yoga we act like our arms are intended to bear weight just as our legs are. This is not the case. In fact the shoulder is not really one joint, but a complex that includes three joints: the sternoclavicular joint (collarbone at the sternum), acromioclavicular joint (shoulder blade at the end of the collarbone) and the glenohumeral joint (arm bone at the shoulder blade). The glenohumeral joint has the greatest freedom of movement of all our extremities which can be advantageous when trying to achieve Upward Bow Pose /Dhanurasana, but can also predispose us to injury. The arm bone ends in a ball-like shape that fits into a socket in the shoulder blade. The shoulder blade sits on the rib cage and hooks over the top to connect with the collarbone forming a small ligamentous attachment. The only other bony point of attachment for the shoulder is at the sternoclavicular joint, where the collarbone then meets the sternum. Otherwise the bones are essentially free floating, under the protection of ligaments and muscular attachments.
The Rotator Cuff: More like a rotator crew
The rotator cuff is one of these protective muscular groups. The name is misleading though. It is not one singular cuff, but a group of four muscles that each exert a supportive role in four different directions on the glenohumeral joint. The supraspinatus muscle sits in the top portion of the shoulder blade and resists downward motion of the arm bone. The infraspinatus and teres minor sit in the bottom portion of the shoulder blade and resist backward motion. The subscapularis muscle is on the opposite side of the shoulder blade, in contact with the rib cage, and resists forward motion of the arm bone.
Two of these muscles are vulnerable to pinching or impingment: the supraspinatus muscle and the subscapularis muscle. Overhead movements with the arms or repetitive pushup /chaturanga motions can contribute to this injury, causing the tendon of the muscles to become pinched between bone. We can avoid this by using a certain amount of scapular retraction when we move. Retraction is the action of the shoulder...
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