There are two possible reasons for the left shoulder not to lift up: First, frozen shoulder. Frozen shoulder can often appear as a limitation of shoulder joint activity in all directions, especially a limitation of shoulder joint lifting function activity. Secondly, rotator cuff tears are most commonly seen in the elderly. When there is a bone spur of the acromion, a spur of the acromion and a large nodule hitting each other, it will lead to a tear of the rotator cuff between them, and then the shoulder joint lifting function will be obviously limited. If the rotator cuff is torn, then arthroscopic surgery should be considered.