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Shoulder Mechanics

The shoulder is mechanically the most complex joint in the body. Think about the motion available to us through movement of the shoulder. Reaching behind your back, into overhead spaces and making a whole circle to perform the "windmill".

Given the motion available through the shoulder there is a lot of opportunity for injury when there is muscle weakness or joint tightness. The rotator cuff is one of the integral components in maintaining this joint stability at the shoulder. The rotator cuff surrounds the head of the Humerus (upper arm bone) and keeps the shoulder pulled into the small socket. Since the rotator cuff is attached to the shoulder blade (Scapula) the muscular stability between the Scapula and the ribs is also important for correct movement of the shoulder joint.

The rotator cuff is made of up 4 muscles including the Infraspinatus (under the spine of Scapula), Subscapularis (under the Scapula), Teres Minor (back of shoulder to side of Scapula) and Supraspinatus (above the spine of scapula). The Supraspinatus is the most commonly injured muscle when referring to a torn rotator cuff tendon. This is due to the position of the Supraspinatus tendon below the bone at the tip of the shoulder called the Acromion.

When reaching overhead or out to the side the Supraspinatus can be compressed or pinched between the Acromion and the head of the Humerus. This phenomenon is called impingement syndrome. When performing repetitive shoulder press at the gym or performing repeated reaching activity at work a person may start to feel twinges of pain at the top of the shoulder. This pain on reaching indicates beginning stages of impingement syndrome.

In order to minimize the chance of impingement, and in some cases prevent shoulder problems, regular shoulder strengthening (and stretching) is recommended. Since reaching overhead is the cause of most impingement and tendon problems, then strengthening the muscles that hold the head of the humerus into place during movement is important. The recommended strengthening for prevention is to load (work out) the shoulder extensors (Latissimus dorsi and Teres Major) and rotator cuff including shoulder rotation, abduction and adduction.

To learn more about a preventative program or treatment for a painful shoulder, contact Ted at Back In Action Physical Therapy.