Recently, we have encountered many patients who came to the clinic with “frozen shoulder”. After being treated at other hospitals, the patients took oral medication and functional exercises as ordered by their doctors, but not only did they have no effect, but their symptoms worsened. In fact, these patients are not suffering from “frozen shoulder”. This indicates that doctors and patients in our region still have a superficial understanding of shoulder diseases. Patients who visit the doctor with shoulder pain are habitually diagnosed with “frozen shoulder”, but in fact, there are many other causes of shoulder pain. In fact, there are many other causes of shoulder pain. “Shoulder impingement” is one of these causes, and it is more common than frozen shoulder. The following is a brief overview, which we hope will be helpful to our patients. Frozen shoulder is an adhesive capsulitis that causes stiffness of the glenohumeral joint. It is characterized by pain around the shoulder joint and reduced active and passive mobility of the shoulder joint in all directions. It is also known as frozen shoulder and is most common in middle-aged and elderly people over 40-50 years old, who often have a history of wind-damp cold attack or trauma. It is more common in women and is commonly referred to as “frozen shoulder”. There are no strict diagnostic criteria for frozen shoulder, but the recommended criteria are: progressive shoulder pain and decreased mobility, especially limited supination; pressure pain around the shoulder, especially in the long head tendon groove of the biceps; muscle spasm or muscle atrophy around the shoulder; no abnormalities on x-ray and laboratory tests; MRI of the rostro-humeral ligament; the frozen shoulder can be diagnosed when other causes are excluded. There are 3 features in the overall pathogenesis of frozen shoulder: ① the soft tissues surrounding the joint capsule are eventually invaded; ② the development of lesions is not uniform, not all tissues have equal pathological changes; ③ the progression of pathological changes is reversible. The entire course of frozen shoulder can be divided into three phases: the beginning phase, the freezing phase, and the thawing phase. The beginning phase is characterized by uncomfortable and binding sensations in the shoulder joint. The pain may be limited to the anterolateral aspect of the shoulder joint or may extend to the point of resistance of the deltoid muscle. The shoulder joint gradually becomes stiff and painful. The pain during the freezing phase can be mild or severe, and is characterized by increased pain at night which affects the patient’s sleep. When the shoulder joint moves, it can cause strong pain and muscle spasm, so that the movement of the shoulder joint can be completely restricted, as if the hand is frozen. During the thawing phase, the pain is mild, the shoulder joint starts to relax gradually, and the glenohumeral joint gradually regains more movement, but in some cases, the function of the shoulder joint is only partially restored or is tense and immobile. Subacromial impingement is a common cause of shoulder pain, much more common than frozen shoulder. Subacromial impingement syndrome, also known as shoulder impingement syndrome, is most commonly caused by the soft tissues between the acromion, rostroscapular ligament, and the humeral head impacting on the acromion and rostroscapular ligament, causing aseptic inflammation of these soft tissues and causing pain and sometimes even impingement. The main manifestations of impingement syndrome are shoulder pain, pain at night, waking up in pain, and disruption of sleep: difficulty in pointing out a clear site of pain: difficulty in raising the arm over the head. When the arm is raised diagonally in front of the head, no matter how hard one tries, the arm does not move as if someone is pulling the sleeve of the armpit tightly. Shoulder impingement syndrome is more common in younger athletes and middle-aged adults. Rotator cuff tears are more common in patients over the age of 40 with shoulder pain. It is mostly due to acute trauma and regular over-exercise, such as painters, warehouse shelf workers or construction workers who are overloaded with work, swimmers or baseball pitchers or tennis players. The main differences between this condition and frozen shoulder are: 1) there is often no obvious fixed pressure pain; 2) the main manifestation is limited abduction of the shoulder joint, which may be combined with decreased internal rotation of the shoulder; 3) the external rotation of the shoulder joint is mostly normal, which is an important basis for differentiation from frozen shoulder; 4) the painful arc of 60-120 degrees of shoulder abduction, when the subacromial shoulder gap is closest to the supraspinatus tendon; 5) positive impact provocation test (provocative test). provocative test). Neer test: The examiner fixes the shoulder joint with one hand, keeps the shoulder joint in internal rotation with the other hand, makes the tip of the thumb face down, and the pain occurs in forward flexion over the top, the mechanism is to artificially make the humeral tuberosity and the anterior inferior border of the shoulder peak impact, which induces pain. hawkins test: The shoulder joint is internally flexed 90 degrees, the elbow joint is flexed 90 degrees, and the forearm is kept horizontal, the examiner forces the patient’s forearm down to cause the shoulder joint The mechanism of this test is to artificially cause the posterior and lateral aspects of the greater tuberosity of the humerus and the supraspinatus tendon plexus to strike the “rostral shoulder arch” (the acromion, rostral process, and rostral shoulder ligament form the rostral shoulder arch). The pain arc, NEER sign, and Hawkins sign are called the triad of impingement of the acromion. In addition, MRI can clearly show the reduction of the subacromial space, inflammatory changes in the bursa and injury and degeneration of the rotator cuff. The two disorders differ in terms of mechanism of occurrence, symptoms, and regression, and they are treated in opposite directions. If a patient with impingement of the rotator cuff is diagnosed with frozen shoulder and over-exercises, it will inevitably cause an increase in impingement symptoms and eventually lead to rotator cuff tears and instability of the rotator joint, causing more pain to the patient. Therefore, the specialist must identify the two diseases in order to really treat the patient correctly. Patients should have a better understanding of both diseases to reduce the unnecessary payment during medical treatment.