The main difference between subacromial impingement (SIS) and “frozen shoulder” is that the range of motion is less restricted than that of “frozen shoulder”, and the pain is most pronounced at 60-120° of abduction. Positive Hawkins impingement test. Subacromial impingement (SIS) refers to the repeated impingement between the greater tuberosity of the humerus and the rostral arch of the shoulder during shoulder supination, resulting in subacromial bursitis, rotator cuff degeneration and tearing, causing shoulder pain and impaired movement. The subacromial space, also known as the supraspinatus outlet or supraspinatus space, is bounded by the rostral arch, which consists of the inferior border of the acromion, rostral shoulder ligament and rostral process, and the inferior border, which includes the greater tuberosity of the humerus and the upper part of the humeral head, and in the subacromial space are the rotator cuff tendon, the long head of the biceps tendon, the subacromial and subdeltoid bursae and the upper part of the glenohumeral capsule. During the supination of the upper extremity, the greater tuberosity moves closer to the acromion, narrowing the gap, which can be caused by pathological changes in any of the tissues. The main manifestations: Pain – mainly around the acromion, radiating to the deltoid stop (one palm distance from the shoulder), pain is most pronounced at 60-120° of abduction, sleepless at night, unable to lie down on the affected side. Shoulder joint movement is limited. Shoulder joint pain develops gradually, from the shoulder to the forearm, and the pain increases when lifting or holding objects, and nocturnal pain may occur. Weakness of the upper extremity and inability to perform movements such as putting the hand behind the body when movement is limited. In severe cases the loss of movement may result in a frozen shoulder. In acute bursitis, there is significant tenderness in the shoulder. There is restriction of movement and pain in all directions of the shoulder joint. The main treatment is early and adequate rest for the shoulder of the affected limb, avoiding supination movements and not premature activities, performing gradual shoulder muscle training, regular treatment at the rehabilitation department may be used, not abusing violent manipulation or massage therapy to prevent rotator cuff tear; some physical therapy including subacromial closed injection and physiotherapy. If the above treatment is not effective, arthroscopic minimally invasive treatment can be used with obvious results.