There are many sources of pain. One way of dividing these sources of pain is to divide them into two groups, nociceptive pain and neuropathic pain. How pain is treated depends in large part upon what type of pain it is.
Examples of nociceptive pain are a cut or a broken bone. Tissue damage or injury initiates signals that are transferred through peripheral nerves to the brain via the spinal cord. Pain signals are modulated throughout the pathways. This is how we become aware that something is hurting.
Neuropathic pain is pain caused by damage or disease that affects the nervous system. Sometimes there is no obvious source of pain, and this pain can occur spontaneously. Classic examples of this pain are shingles and diabetic peripheral neuropathy. It is pain that can occur after nerves are cut or after a stroke.
Most back, leg, and arm pain is nociceptive pain. Nociceptive pain can be divided into two parts, radicular or somatic.
Radicular pain: Radicular pain is pain that stems from irritation of the nerve roots, for example, from a disc herniation. It goes down the leg or arm in the distribution of the nerve that exits from the nerve root at the spinal cord. Associated with radicular pain is radiculopathy, which is weakness, numbness, tingling or loss of reflexes in the distribution of the nerve.
Somatic pain: Somatic pain is pain limited to the back or thighs. The problem that doctors and patients face with back pain, is that after a patient goes to the doctor and has an appropriate history taken, a physical exam performed, and appropriate imaging studies (for example, X-rays, MRIs or CT scans), the doctor can only make an exact diagnosis a minority of the time. The cause of most back pain is not identified and is classifies as idiopathic. Three structures in the back which frequently cause back pain are the facet joints, the discs, and the sacroiliac joint. The facet joints are small joints in the back of the spine that provide stability and limit how far you can bend back or twist. The discs are the “shock absorbers” that are located between each of the bony building blocks (vertebrae) of the spine. The sacroiliac joint is a joint at the buttock area that serves in normal walking and helps to transfer weight from the upper body onto the legs.
Fluoroscopically (x-ray) guided injections can help to determine from where pain is coming. Once the pain has been accurately diagnosed, it can be optimally treated.