1. What is rotator cuff? The rotator cuff is the collective name for four important muscles around the shoulder joint. These four muscles are the supraspinatus, infraspinatus, subscapularis and teres minor. The main function of these four muscles is to govern the movement of the shoulder joint in all directions. 2.What is rotator cuff injury? A rotator cuff injury is a tear of the rotator cuff tendon. The tendon is the part of the muscle that is connected to the bone. When a person is young, the tendon is of good quality and tough, so it is difficult to tear. However, when a person gets older, the quality of the tendon decreases rapidly and wear and tear occurs with the surrounding bones due to years of use, so it is easy to tear the tendon. Younger patients may also experience upper extremity weakness after an apparent trauma that causes the tendon to rupture. 3.What are the symptoms of rotator cuff injury? The most typical symptoms of rotator cuff injury are twofold: pain in the shoulder joint and weakness in the shoulder joint. Some patients may wake up with pain in the shoulder joint when they are sleeping. If weakness is the most significant symptom, the patient may feel weakness in the affected limb and have difficulty lifting the injured side of the upper limb on his or her own. However, the bad hand can be lifted with the good hand. 4.How to diagnose rotator cuff injury? You should go to the hospital for examination. An experienced doctor can get a preliminary impression of whether a rotator cuff injury may exist by examining the patient’s upper extremity movement. However, an MRI is often needed to confirm the diagnosis. 5.How is a rotator cuff injury treated? Because the tendon is torn, and because the tendon itself is elastic, there is often significant retraction after the tear, so conservative treatments such as injections and medications are not effective for rotator cuff injuries. Treatment generally requires surgery to sew the torn tendon back to the bone. 6.What are the surgical options for rotator cuff injuries? Earlier surgery often required a large incision to open the joint and repair the tendon. Nowadays, due to the increasing maturity of arthroscopic technology, this type of surgery can be performed under the microscope, which greatly reduces the trauma to the patient and allows for a faster return to shoulder function.