Shoulder Impingement

Impingement is one of the most common causes of pain in the adult shoulder. It results from pressure on the rotator cuff from part of the shoulder blade (scapula) as the arm is lifted.

The rotator cuff is a tendon linking four muscles: the supraspinatus, the infraspinatus, the subscapularis, and the teres minor. These muscles cover the "ball" of the shoulder (head of the humerus). The muscles work together to lift and rotate the shoulder.

The acromion is the front edge of the shoulder blade. It sits over and in front of the humeral head. As the arm is lifted, the acromion rubs, or "impinges" on, the surface of the rotator cuff. This causes pain and limits movement.

Full explanation HERE

So my shoulder is impinged ;-) one of the strangest injuries I've ever had, got a shoulder strap on the way to help things along and its amazing how useful frozen peas can be when needed.