Pain drawings are a common tool used with back pain patients. Different drawings have various meaning and uses. Some are just used to show where the pain is located. Filling out the form each time gives the doctor an idea if the pain is changing. The drawings can map out other symptoms, too such as numbness or tingling.
Some drawings are combined with choosing words to describe the pain. The McGill Pain Questionnaire is such a tool. It can help identify the source of pain. For example, pain described as "throbbing" could be a sign of vascular disease. The doctor may be able to diagnose the problem by looking at the location of the pain and the description at the same time.
These types of tools can also point out when there's an emotional or psychologic response to back pain. Pain drawings by themselves aren't able to predict anxiety or depression. They are much more useful when combined with other measures.