Collectively, the tendons of the shoulder are called the rotator cuff . In addition to these structures, the shoulder contains two bursae , which are soft, fluid-filled, closed structures that cushion the movement of muscles, tendons and bones associated with the shoulder joint. It allows people to hunch the shoulder forward, move it backward and either rotate the arm or move it like a hinge, away from the body. Because of the range of motion that the shoulder allows, it is a relatively unstable joint. To remain stable, the shoulder must be anchored by its muscles, tendons, and ligaments.
Some shoulder problems result from the disruption of soft tissues like the tendons and ligaments.
Other problems arise from degenerative processes, in which tissues gradually break down and no longer function well. Shoulder pain may be localized to the joint itself, or may be felt in areas around the shoulder or down the arm. Doctors initially evaluate a patient for shoulder pain by listening to the patient's description of the pain, asking questions, and performing a physical examination. They may also perform tests such as x-rays, arthrograms , or magnetic resonance imaging . These conditions are closely related, and may occur alone or in combination.