Pain generated by the spinal disc is quite often misunderstood-partly because health professionals often do not agree on what spinal disc pathology is, and partly because the disc problems are not always well explained to (or understood by) patients.

There are many different terms to describe spinal disc pathology (such as pinched nerve, herniated disc, bulging, ruptured or slipped disc, disc protrusion, or degenerative disc disease), and these terms tend to be used somewhat differently among health professionals. The goal of this article is to help you better understand how the disc can cause pain and what’s important to know about it.

Disc problems do not directly correlate to pain

While it seems contrary to common sense, the severity of pain from a lower back injury does not always correlate to the amount of physical damage. For example, muscle spasm from a simple back strain can cause excruciating back pain, whereas a large herniated disc can be completely painless. Additionally, back pain is a very complicated personal experience. Many disc abnormalities seen on MRI scans are actually painless, and other factors – both physical and psychological – often contribute to a person’s experience of pain.

There is a lot of overlap of nerve supply to most of the structures in the spine (discs, muscles, ligaments, etc), so it is difficult for the brain to distinguish between injury to one structure versus another. For example, a herniated disc can feel identical to a bruised muscle or ligament injury. For this reason, it is very difficult to self-diagnose your pain. It is best to have a qualified physician first take a thorough medical history and physical exam, discuss your symptoms, and if necessary conduct diagnostic tests, in order to try to distinguish the underlying condition causing your pain.

It is best to get a firm clinical diagnosis

Please keep in mind that the terms for disc problems (such as herniated disc, pinched nerve, bulging disc, slipped disc, ruptured disc, etc.) refer to radiographic findings seen on a CT scan or MRI scan. While radiographic findings are important, they are not as meaningful in determining the source of the pain (the clinical diagnosis) as your specific symptoms and the spine specialist’s findings on physical exam. Usually, the key factor in the clinical diagnosis is to determine if you have pinched nerve or if the disc space itself is generating the pain. A pinched nerve will generate radicular pain (nerve root pain or sciatica), and disc pain will generate either referred pain or axial pain.

The diagnosis guides the treatment decisions

It’s important to accurately diagnosis the pain generator, because the type of pain created by the spinal disc dictates the type of treatment, and the treatments for the different diagnoses vary considerably. Two of the more common disc problems include:

• Herniated disc.If the outer portion of the disc (annular fibers) stretches or ruptures, the inner material of the disc may be allowed to bulge or extrude (herniated) out of the disc. This condition may also be referred to as a pinched nerve, slipped disk, bulging disc, etc. When this happens, the inner material of the disc can come in contact with and irritate the adjacent nerve root, causing pain to run along the path of the nerve – either along the sciatic nerve down the leg (lumbar disc herniation or sciatica) or arm (cervical disc herniation). The inner material of the disc is filled with inflammatory proteins, so even a small disc herniation that allows the inner disc gel to just touch the nerve can cause a great deal of pain.
• Degenerated disc.As we age, the spinal discs dehydrate and become stiffer. While this is a natural aging process, in some individuals, the degenerating disc can become painful and inflame the well-innervated structures next to the disc (e.g. nerve roots). Also, the disc may be damaged as the result of some trauma, and inner or outer portions of the annular fibers may tear.