Another reason for shoulder impingement syndrome to occur is insufficient elevation of the clavicle. Most of scapular upward rotation is actually caused by elevation of the clavicle at the sternoclavicular joint, so if clavicular elevation is prevented for any reason, shoulder impingement syndrome can occur.
For scapular upward rotation to occur, scapular downward rotator musculature must lengthen. If scapular downward rotation muscles are tight, they might not be flexible enough to allow for scapular upward rotation, thereby causing shoulder impingement syndrome to occur.
Shoulder impingement syndrome is a condition in which the distal tendon of the supraspinatus and the subacromial bursa become impinged between the head of the humerus and the acromion process of the scapula. Following are the six major causes of shoulder impingement syndrome.