The term arthritis literally means inflammation of a joint but is generally used to describe any condition in which there is damage to the cartilage. Damage of the cartilage in the shoulder joint causes shoulder arthritis.
A break in a bone that makes up the shoulder joint is called a shoulder fracture.
The clavicle and end of the humerus closest to the shoulder are the bones that usually get fractured. The scapula on the other hand is not easily fractured because of its protective cover by the surrounding muscles and chest tissue.
Pain in the shoulder suggests a shoulder injury which is more common in athletes participating in sports such as swimming, tennis, pitching and weightlifting. The injuries are caused due to the over usage or repetitive motion of the arms.
Shoulder instability is a chronic condition that causes frequent dislocations of the shoulder joint.
A dislocation occurs when the end of the humerus (the ball portion) partially or completely dislocates from the glenoid (the socket portion) of the shoulder. A partial dislocation is referred to as a subluxation whereas a complete separation is referred to as a dislocation.