The human shoulder is a relatively large joint and the range of motion is actually that of the glenohumeral joint. The normal range of motion is 90 degrees of abduction, 20-40 degrees of adduction, 70-90 degrees of forward flexion, 40 degrees of back extension, 45-60 degrees of external rotation, and 45-70 degrees of internal rotation. If this range of motion becomes smaller in daily life, it is possible to develop a shoulder disorder. For example, if both active and passive movement of the shoulder joint is limited, the patient may be considered to have frozen shoulder, and if the active range of motion becomes less, this is often seen in rotator cuff injuries. In addition, if a patient feels pain in the shoulder joint with reduced range of motion in daily life, he or she should go to the hospital promptly and get a clear diagnosis from the doctor before taking symptomatic treatment.