The biceps muscle is on the front part of the upper arm and has two heads.  Each 'head' turns into a tendon at the top that attaches onto the shoulder blade. The long head goes up the front of the shoulder in a shallow groove, held by a ligament, and then goes over the top of the ball and attaches on the top edge of the socket.  The short head passes to the inside of the ball and attaches to the coracoid process of the shoulder blade.

Given the anatomy of the shoulder and the very small space that the rotator cuff tendons pass through, it is a wonder that people don't have more trouble than they do.  The biomechanics (how the shoulder moves) of the shoulder are further affected by areas that are tight and structures that are weak.  These problems, with movement, can cause the ball to ride up in the socket, causing pinching that can lead to tendonitis.

Impingement refers to the pinching effect on the rotator cuff tendons between the ball of the shoulder and the acromion process - the bony 'roof' over the ball and socket.  There are a variety of factors that can lead to impingement and that must be addressed to correct it.  Click on the heading to see all the FAQs related to impingement.

The shoulder complex in comprised of four joints or articulations: the gleno-humeral (ball and socket), A-C (acromion -shoulder blade- and collar bone), S-C (sternum -breast bone- and collar bone) and S-T (scapula -shoulder blade- and thoracic -rib cage and thoracic spine).  The collar bone attaches to the breast bone, curves forward and then backward as it attaches to the acromion process on top of the shoulder.  Click on the heading link above to view the FAQs for this topic.

When someone separates their shoulder, the injury is to the acromio-clavicular joint.  This is where the shoulder blade's acromion process (projection) attaches to the clavicle (collar bone).  This makes up the bony 'roof' of the shoulder, directly above the ball and socket joint.  The A-C joint is part of the shoulder 'complex'.  

The shoulder joint has a ball (top part of the arm bone, the humerus) that moves in a socket (shallow area on the shoulder blade).  The socket is deepened by a 'rim' of cartilage, called the labrum.  The ball and socket has a capsule (a tough, thick tissue with bands of thicker tissue) that attaches above the socket and below the ball to hold the joint together.