Your shoulder joint has the largest range of motion out of all the joints in your body. This flexibility allows you to hit a backhand swing in tennis, stretch to reach something on a top shelf, or lift heavy items. The shoulder also helps you position your hand for movements such as waving goodbye or using the mouse on your computer.
With this flexibility, however, injury can result — along with a variety of painful problems. The shoulder consists of 3 bones:
Two main joints help your shoulder move easily:
Commonly called the shoulder joint, the glenohumeral joint (def.) helps you move your shoulder forward and backward. It also enables your arm to rotate in a circular manner or move outward.
The glenohumeral joint is composed of the socket on your shoulder blade (glenoid) and the "ball" at the top of your arm bone (the humerus). Uniquely, the ball of the upper arm bone is twice the size of the shoulder blade socket.
One way of picturing this joint is to think of a golf ball on a tee.
The acromioclavicular joint (def.) is located between your shoulder blade (acromion) and your collar bone (clavicle).
The sternoclavicular joint (def.) is another joint in this region that isn’t part of the shoulder joint, but is a bridge between the upper extremity and the back of your rib cage (thorax).
This complex arrangement of bones, muscles, tendons, and ligaments can be injured by an accident or overuse. Disease also can affect the shoulder. When that happens, the pain and lack of mobility can be severe enough to affect your ability to work and enjoy normal activities of daily life.
Learn about common shoulder problems.
The joint with the largest range of motion in your body is the shoulder joint.