Shoulder impingement syndrome is the most common cause of shoulder pain. It is caused by impingement of the rotator cuff on the acromion and greater tuberosity of the humerus after the upper arm is raised. The rotator cuff is composed of the tendons of the supraspinatus, infraspinatus, subscapularis and teres minor muscles, which wrap around the humeral head and serve to lift and rotate the shoulder joint. One of the compressed rotator cuffs is the supraspinatus tendon. Injury to the supraspinatus tendon causes inflammation or tears that cause pain and result in pain and limited motion of the shoulder joint. I. Risk factors and prevention 1. Congenital deformity of the acromion, causing narrowing of the subacromial space against the supraspinatus tendon. 2, Degeneration caused by osteophytes of the acromion resulting in narrowing of the subacromial space impinging on the supraspinatus tendon. 3.People who have been excessively exercising the shoulder joint for a long time, such as swimmers who often do supination, baseball and tennis, as well as construction workers and painters, are particularly prone to injury. 4.Acute injury due to fall with impact on supraspinatus tendon tear. 5, Frozen shoulder causes joint space narrowing during weekday activities or functional exercises that can easily damage the supraspinatus tendon. Symptoms The symptoms may be mild at first. In the early stages, patients do not come to seek medical attention. There may be pain during activity at the beginning of the disease. The pain may radiate from the shoulder to the lateral shoulder or even to the forearm, and may become worse when lifting or holding an object. As the pain progresses, nocturnal pain may develop. Strength or range of motion in the upper extremity may be reduced. It may not be possible to put the hands behind the back and make movements to fasten and unfasten buttons. In severe cases the loss of motion may cause frozen shoulder. In acute bursitis, there may be significant tenderness in the shoulder. There is restriction of motion and pain in all directions of the shoulder joint. III. Diagnosis The diagnosis of shoulder impingement relies on symptoms and signs and imaging. Symptoms: As above, nocturnal pain is a more common symptom. Signs: lateral shoulder, subacromial pressure pain, limitation of shoulder movement, i.e., inability to raise the arm, inability to put the hand behind the back, etc. Imaging: MRI (magnetic resonance imaging) suggests supraspinatus tendon rotator cuff injury, which has characteristic changes according to the reading of an experienced arthroscopist. The supraspinatus exit position should also be taken, suggesting a deformity of the acromion and narrowing of the exit. Special physical examination: 1, pain arc sign: upper arm abduction 0-60° without pain, 60-120° with pain, 120°-180° without pain again. 2.Impact test: It simulates the action of subacromial impingement. A positive result represents that the subacromial tissue has impingement with the acromion and rostral shoulder ligament and causes pain, so it has important diagnostic significance. The specific method is to compress the affected scapula with the hand downward and make the affected shoulder lift upward, so that the large humeral tuberosity impacts with the shoulder peak and causes pain. Stage 1 is also called edema and bleeding stage. It can occur at any age when the shoulder joint is overused and cumulative injury occurs due to over-exertion of the arm, such as painting and decorating of the board wall, gymnastics, swimming, tennis, baseball, throwing, etc. It is a common cause. This stage also includes a history of a one-time simple shoulder injury, such as edema and hemorrhage of the supraspinatus tendon, biceps longus tendon and subacromial bursa following a strenuous torso contact sport or a severe fall. In this stage, although the muscle strength is reduced due to pain, there are no typical symptoms of rotator cuff tears, and physical examination does not easily reveal signs such as painful arc signs and a positive chronic impingement test. Subacromial injection of lidocaine can completely relieve the pain. X-rays generally have no abnormal findings, and arthrography cannot detect the presence of rotator cuff rupture. Stage 2 is the stage of chronic tendinitis and bursal fibrosis. The bursa fibrosis and bursal wall thickening due to repeated impingement under the acromion of the shoulder in middle-aged patients and chronic tendonitis due to repeated injury to the tendon, usually with fibrosis and edema. The thickened bursa and tendon occupy the subacromial space, and the relative narrowing of the supraspinatus outlet increases the chance and frequency of impingement, with painful episodes lasting several days. Shoulder fatigue and discomfort are still felt during the pain relief period, and physical examination is more likely to reveal painful arc signs and positive impingement tests. The main pathological changes are partial or complete rupture of the supraspinatus tendon and the long head of the biceps tendon on the basis of repeated injury and degeneration. The age at which rotator cuff rupture is more likely to occur is after 50 years of age, with a mean age of 52 years for partial tendon ruptures and 59 years for complete ruptures. It should be noted that not all impingement signs lead to rotator cuff rupture and not all rotator cuff injuries are caused by impingement signs. In most cases, the force of injury is actually less than the force required to cause a complete rotator cuff rupture, indicating the importance of the degenerative factors of the tendon itself. Treatment 1. Conservative treatment The patient will be advised to rest and avoid supination exercises. Some oral NSAIDs may also be prescribed. This is the opposite of the treatment of frozen shoulder, where functional exercises are not possible and only suspension and immobilization are the mainstay. 2.Surgical treatment When conservative treatment cannot reduce the pain, it is usually conservative for 2-3 months, and if it does not improve, surgical treatment is recommended. The purpose of surgical treatment is to remove the impingement and create a relatively large space for the rotator cuff. This allows the humeral head to move freely in the subacromial space and lift the upper arm without pain. The most common procedures are subacromial decompression and anterior capsuloplasty. This can be accomplished with arthroscopic surgery and also allows for repair of the injured supraspinatus tendon. Shoulder arthroscopy technique: During arthroscopic surgery, 2-3 puncture holes are made. The shoulder joint is examined with a fiber-optic camera system, and small, delicate instruments are used to perform the surgical operation within the shoulder joint. If the rotator cuff tear is large, an incision can also be performed: a small incision can be made in the front of the shoulder joint so that the acromion and rotator cuff can be seen under direct vision. Most patients with impingement of the rotator cuff have some bone removed from the anterior border of the rotator cuff with some bursal tissue attached. 3. Rehabilitation After surgery the shoulder joint is temporarily immobilized with or without a brace depending on the situation. Then you will start to exercise and use the shoulder joint under the guidance of your doctor according to the follow-up. Your doctor will provide a rehabilitation plan based on your needs and the findings from the surgery. This includes exercises to restore range of motion and strength to the shoulder joint. Pain relief is usually evident and function needs to be restored with exercise.