Three bones come together to form the shoulder. These bones are the collar bone (Clavicle), the shoulder blade (Scapula) and the upper arm bone (Humerus). The acromian, a part of the shoulder blade, forms the top of the shoulder.
The shoulder is made up of four separate joints. The interrelated action of these four joints allows the complex and extremely wide range of movements of the shoulder.
The ball-and-socket joint or glenohumaral joint, is the main joint of the shoulder. This joint is reinforced and assisted in its movement by the rotator cuff, a combination of four tendons and associated muscles. The muscles arise on various parts of the shoulder blade, and their tendons attach to the upper arm bone. (Tendons are stringy tissues that attach muscles to bone).
A “ball” at the top of the upper arm bone (The humerus) fits neatly into a “socket” called the glenoid, which is part of the shoulder blade (scapula). But unlike the hip joint, where the ball sits in a deep well protected socket; the shoulder socket is very shallow. The shallow socket of the shoulder is given some extra depth by a structure called the labrum. The labrum is actually a thickened firm tissue that is attached to and surrounds the main glenohumeral joint. It provides stability to the shoulder joint when it is lifted up in a movement like throwing. The surrounding ligaments, muscles and tendons that move the shoulder joint, help to keep it stables. One of the tendons of the biceps muscles runs through the shoulder joint and further helps to stabilize the joint. Because of this anatomy, the shoulder is the most frequently dislocated major joint in the body.
Between the rotator cuff and the bony arch of the acromion lie two fluid-filled sacs called bursae. They protect the rotator cuff and allow smooth movement of the tendons over the bone.
It is also prone to a variety of other injuries and chronic problems that can be painful, cause sleep disturbances and hinder a person’s ability to perform ordinary tasks or sporting activities.
Most problems in the shoulder involve the muscles, ligaments and tendons rather that the bones. Shoulder injuries can be caused by sports activities that involve excessive overhead motion (Such as swimming, tennis and cricket). But they can also be the result of everyday activities like paining, hanging curtains and gardening. The arthroscope is the most accurate diagnostic tool for confirming shoulder problems.