The shoulder joint is the most flexible joint in the body, but this high degree of flexibility comes at the expense of some stability. Several bones and their connecting soft tissues (muscles, ligaments, tendons) work together to produce the motion of the shoulder joint. These components interact with each other within the limits of maximum motion to maintain the integrity of the shoulder joint. Each component of the shoulder joint contributes to the motion and stability of the shoulder joint. Certain tasks or sports are extremely demanding on the shoulder joint, and when the limits of shoulder motion are exceeded and/or excessive forces are applied to one of the components, a shoulder injury will result. Shoulder injuries are more common in young people, athletes and older populations. In all of these groups, there are many causes of shoulder pain. Two very common injuries in the narrow bony spaces of the shoulder are localized irritation and inflammation called rotator cuff impingement syndrome and tendon injuries called rotator cuff tears. These two conditions can exist independently or together. Rotator cuff tears are most likely caused by rotator cuff impingement and aging changes in the rotator cuff tendons. Rotator cuff impingement syndrome or subacromial impingement syndrome occurs when the rotator cuff tendons and subacromial bursa are compressed in a narrow space under the acromion, resulting in swelling and inflammation of the rotator cuff tendons and subacromial bursa. This compression is more severe when the arm is raised away from the torso and the symptoms are most pronounced. Minor rotator cuff injuries can progress to rotator cuff impingement over time, and repeated repetitive motion of the shoulder joint can also lead to inflammation of the subacromial bursa. The specific shape of the acromion can make some people more susceptible to impingement between the acromion and the bursa; as people age and develop arthritis, bone spurs can form on the acromion, further narrowing the subacromial space. Rotator cuff impingement is more common in older adults who play sports or work in an overhead position. If calcium deposits occur in one of the rostro-capital ligaments, they can also lead to spur formation. Rotator cuff impingement can be of three degrees: 1. I° is characterized by inflammation and thickening of the subacromial bursa and rotator cuff tendons. 2, II° is characterized by progressive hyperplasia and scar formation of the subacromial bursa. 3, III° is characterized by more pronounced rotator cuff degeneration, degeneration and tearing.