Poor Posture
Studies show that poor posture is one of the most common causes of shoulder blade pain. A poor posture causes overload in the spine and exerts an unequal amount of stress on the structures around the spine. In most cases, you may have to change postures continuously when working. If you are working as an IT professional, or bending continuously while doing chores, you are more likely to experience shoulder blade pain. A poor posture can overload the muscles of the upper back and cause pain beneath the shoulder blade.
Fracture
Pain beneath the shoulder may occur due to fracture [1] of the shoulder blade. The pain may also spread to sites around the shoulder blade, and limit the range of arm movement.