With this common knowledge, people are used to classifying many shoulder-related diseases as “frozen shoulder”. Many people think it is frozen shoulder when they have shoulder pain, so they rush to exercise and physical therapy, thinking that they will recover. However, in many cases, rotator cuff tears are the real culprit. Due to the lack of knowledge and incorrect diagnosis, many patients go further and further down the road of treatment. There is a difference between rotator cuff injury and frozen shoulder, but due to the lack of experience of the public and some doctors, they often think that shoulder pain is frozen shoulder, which leads to misdiagnosis and mistreatment. Since both frozen shoulder and rotator cuff injury have a history of shoulder joint limitation and pain, it is difficult to differentiate them. If you experience weakness in lifting the affected limb and are unable to lift it over the head, or if you experience significant pain when lifting it over the head, you should be highly suspicious of rotator cuff injury and need to go to an orthopedic clinic to determine whether there is a rotator cuff injury. ”The rotator cuff, as the name implies, is the four important muscles around the shoulder joint. They are like “cuffs” around the shoulder joint, which protect the shoulder joint and play a role in stabilizing the shoulder joint when the upper arm is raised. A rotator cuff injury is a tear of the rotator cuff tendon, so when you lift your hand, the rotator cuff cannot protect the shoulder joint and you feel pain. Since the shoulder joint is the joint with the largest range of motion in the body, it is also the most unstable joint. Age-related factors cause degeneration of the tendon, and the rotator cuff muscle strength decreases after a traumatic injury or long-term chronic wear and tear that leads to rotator cuff tears. It can be said that when a person is young, the tendons are tough and strong, so it is difficult to tear them, but when they get older, the quality of the tendons decreases and they are worn out with the surrounding tissues over the years, and when they are stretched during sports, it is easy to tear them.