To better understand the problems and pain associated with the shoulders, it helps to begin with an explanation of the structure of the shoulders and how they operate.
The shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone). Two joints create shoulder movement. The acromioclavicular (AC) joint is located between the acromion and the clavicle.
The glenohumeral joint, commonly called the shoulder joint, is a ball and socket type joint that helps move the shoulder forward and backward and allows the arm to rotate. The capsule is a soft tissue envelope that encircles the glenohumeral joint that is lined by a thin, smooth synovial membrane.
The shoulder is easily injured causing shoulder pain because the ball of the upper arm is larger than the shoulder socket that holds it. To remain stable, the shoulder must be anchored by its muscles, tendons, and ligaments.
Although the shoulder is easily injured during sporting activities and manual labor, the primary source of shoulder pain appears to be the natural age-related degeneration of the surrounding soft tissues such as those found in the rotator cuff. The incidence of rotator cuff problems rises dramatically as a function of age and is generally seen among individuals who are more than 60 years old. Overuse of the shoulder can lead to more rapid age-related deterioration.
Shoulder pain may be localized or may be felt in areas around the shoulder or down the arm. Disease within the cervical spine of the neck also may generate shoulder pain that travels along nerves to the shoulder.