A protruding bone on both shoulders may be due to several reasons: 1. It may be a normal bony protrusion. In the shoulder joint itself, there is a series of normal bony protrusions like the shoulder peak, scapular post, acromioclavicular joint and so on. If you are thin, the bony protrusions will be very obvious, and they will appear in both shoulders at the same time, and they are very symmetrical. In addition, when doing a particular position or movement, the protrusion may become more pronounced. 2. This condition may be caused by a local occupational disease. For example, a bony protrusion on both shoulders that is asymmetrical may be caused by a bone tumor. 3. This condition may also be caused by a bilateral acromioclavicular joint lesion. For example, a bilateral subluxation or inflammation of the acromioclavicular joint may cause a significant bony protrusion and lead to the misconception that a new bone has grown there.