The protrusion of the bone under the right clavicle may be caused by the following reasons: 1. It may be caused by the presence of spinal or thoracic deformities, such as the presence of congenital scoliosis, which may lead to asymmetry in the thoracic area, which may make the bony protrusion under the right clavicle, such as the rostral process or the acromioclavicular joint appear more prominent. 2. The rostral prominence may be caused by an old injury to the rostral process. 3. It may be caused by a lesion of the right acromioclavicular joint, such as the intersection of the clavicle and scapula on the right side. If there is a dislocation of the acromioclavicular joint or a fracture around it, it may cause an obvious bony protrusion.