The common causes of two shoulders not being the same height are bad posture, neck lesions, bone deformities and old injuries, as follows: First, bad posture: There are many patients who have such a change in appearance due to their own bad posture. Many patients are used to shrugging their shoulders to one side or keeping the muscles of one shoulder tense for a long time, which may lead to unevenness of both shoulders. Second, neck lesions: Some patients may have lesions in the neck muscles, such as sloping neck, which may lead to uneven shoulders. Third, bone deformities: Some patients may also have bone deformities related to the spine, which may lead to such shape changes. Patients with scoliosis, for example, may have uneven shoulders. Fourth, old injury: Some patients may have old injury, such as old clavicle fracture, which may lead to such shape change.