Sudden soreness of the shoulder. In this case, we should consider acute sprain of the shoulder, rotator cuff injury, frozen shoulder and other reasons, as follows: First, acute sprain of the shoulder: when doing sports, such as playing tennis or badminton and other over-the-shoulder sports, it is very easy to cause strain of the deltoid muscle, so there will be sudden soreness of the shoulder. Second, rotator cuff injury: also when doing over-the-shoulder sports, rotator cuff injury or rotator cuff tear will suddenly cause soreness in the shoulder joint, and may be accompanied by weakness in lifting the shoulder. At this time, an MRI should be performed to clarify whether the rotator cuff is torn. Third, frozen shoulder: When frozen shoulder attacks occur, there will often be pain in the shoulder joint, especially under the stimulation of cold factors, such as cold wind, cold water stimulation and other cold invasion, there will be a sudden soreness and pain in the shoulder.