If you cannot raise your arm out to the side and above your head there is likely a supraspinatus muscle tear. If that injury is a complete tear then you will need surgery, if a partial tear therapy will help. The shoulder is a very complex joint and relies on the shoulder blade, the scapula for added stability. When the shoulder is raised to the side most people will incorrectly use the trapezius muscle or the levator scapula muscle to complete the movement. This can be seen when the shoulder raises up as the arm moves. It will look like the person is shrugging. The correct way to move the shoulder arm is to keep the shoulder down and use the supraspinatus muscle while keeping the shoulder blade pinned against the rib cage. Over time this dysfunction will place stress on various structures in the shoulder causing tearing, degeneration and bursitis.