1.Symptoms of rotator cuff injury Acute injury has a sudden and severe pain at the top of the shoulder, with a tearing or fracturing sensation, and the pain is maintained for a number of days, and then gradually decreases. After the acute symptoms subside, the pain extends to the deltoid stop area. Because of the pain that occurs when the upper arm is abducted over the shoulder, patients tend to hang the upper hip over the body delete. Most patients present with insidious progressive shoulder pain and weakness, often spreading to the deltoid stop area, with pain increasing at night. Pain in the shoulder joint can lead to a succession of limitations in active and passive activities. 2. Clinical signs of rotator cuff injury (1) Tenderness: Tenderness can be felt at the tear in the acute stage, and afterwards, the pressure pain there can still be palpable. When the superior muscle is involved, the pressure pain is at the top of the greater tuberosity. Due to the involvement of the inferior muscle, the pressure pain is on the lateral side of the top of the greater tuberosity. When the laceration affects the biceps tendon, tenderness is at the inter-nodal groove. When the subscapularis tendon is torn the tenderness is anteriorly below. (2) Popping: The patient may feel a popping sound when lifting and rotating the upper arm. The popping sound can be felt when the hand is placed on the patient and made to lift and rotate. The popping sound can be aggravated by passive movement. (3) Muscle atrophy: 2 to 3 weeks after the acute phase, there will be muscle atrophy in the upper and lower muscles, especially in the lower muscles. The longer the degree, the more serious, the longer the small round muscle and trapezius muscle can also be called obvious atrophy. The deltoid muscle is flattened by atrophy, but not as significantly as the inferior and superior muscles. (4) descending and depression: when the tear is severe there is often augmentation or furrow depression. The augmentation is a large tuberosity protrusion, with some tendon cuff stops still attached. The depression is the defect left after the rotator cuff tear. In extension, the augmentation is directly in front of the acromion margin, and in abduction the augmentation or depression passes through the rostral shoulder arch and causes a popping sound. (5) Dysfunction of the acromioclavicular joint: when the tear is severe, the patient cannot abduct the upper arm and it is replaced by shrugging the shoulder. (6) If the rotator cuff injury is mild, the pain is caused when the torn part is squeezed under the rostral shoulder ligament when the upper arm is abducted, which is called positive shoulder pain arc syndrome: the patient is examined in the standing position, and the affected limb is abducted by fixing the subscapularis angle. The pain is worst between 80° and 120°, when the distance between the greater tuberosity and the acromion is nearest to the acromion, and decreases beyond l20°. When the upper arm is lowered, pain also occurs in this range. In addition to rotator cuff tears, shoulder pain arc syndrome can also occur due to calcification of the supraspinatus tendon, inflammation, and subacromial bursitis. (7) Patients with rotator cuff injury have reduced arm lifting strength. Although the patient can freely abduct the upper arm, there is difficulty in abduction or forward flexion as long as light resistance is applied. If the disease is prolonged, arm rotation or elevation activities may be reduced or even disappear.