A Pain management doctor specializes in diagnosis and treatment of the chronic pain that is the pain which has been bothering you for a very long time. The pain physician helps you identify the cause of your pain. It is done through detailed history, examination followed by some blood test and radiological test like X ray, CT scan or MRI if needed. After identifying the cause of pain, they can come up with a plan which works best for you. If you have been taking pain medication for a long time and there is no or only temporary relief you get, the pain physician can do some injections which can help. Since these injections focus on the cause of pain, the relief is quick and much more than what you get from medications. Also, these injections do not have any long-term side effects.
Pain management doctors also specializes in treating the cancer pain. Since pain due to cancer comes from multiple causes like cancer itself, areas its compressing on, as a side effects of chemotherapy or radiotherapy, hence the treatment has to be multimodal.