Lower back pain is a common injury seen at my practice, both in the sporting and non-sporting population. There are multiple pain producing tissues of lower back pain (muscles, facet joints, ligaments, fascia etc) however, two of the most commonly affected tissues are the disc and nerve. This short article should give you an idea of the difference in symptoms between the two structures.
What is the disc?
The Intervertebral Disc, is made up of two different tissues…On the outside, we have a thick, tough ring called the Anulous Fibrosus, and on the inside, we have a “jelly-like” material called the Nucleus Pulposus. The disc sits between two vertebral bodies and is not a true “joint”, but acts as more of a shock absorber and allows for one vertebra to move on another. I often tell my patients to imagine a thick layer of jam between two pieces of hard toast. If you squash the toast on one side, the jam gets pushed out the opposite side. For example, when you bend forwards, the jelly inside gets squashed and moves backwards, allowing the two vertebra to move, but not “collapse”.
The problem occurs when we put too much loading through the disc, and then force the jelly in a certain direction. A typical example of this is when you bend over to move a heavy box and then you are unable to stand up straight due to the pain in your lower back. The position of the jelly combined with the added weight of the box causes the jelly to be forced backwards and it pushes into the outer ring (see images 1 and 2 below).
This is referred to as a DISC BULGE and can be compounded by a small amount of wear-and-tear of the outer ring (small tears and cracks with ageing). Symptoms of a disc bulge include a broad “band” of pain across the lower back (and sometimes into the buttock) as well as sharp pain with changing positions (sit to stand). Coughing and sneezing are often painful (due to the increase in abdominal pressure, pushing the disc material out further). Usually these disc bulges heal well with physiotherapy techniques (we try to gently squeeze the damaged tissue back in) and anti-inflammatories, and depending on the extent of the damage, can take anywhere from a few days to a few weeks to heal…
If the injury is more severe, we speak of a DISC HERNIATION (Image 3- it has now broken through the outer ring) OR DISC SEQUESTRATION (image 4- part of the jelly has “broken away”). At this point, the inflamed disc and its material often starts to push on the nerve exiting the spine, and now we also have NERVE ROOT IMPINGEMENT.
This is usually accompanied by pain, numbness, weakness and pins/needles of the affected nerve root (pain usually radiates down a part of/or the whole leg), and the pain in the leg usually outweighs the pain in the lower back. These injuries take longer to heal and conservative therapy does have a high rate of recovery, however surgery is sometimes needed.
A nerve can also get trapped where it exits the spine through a little opening called the foramen. Generally this happens in older patients with arthritic degeneration, where the opening becomes narrower due to extra bone formation, enlarged joints and narrowed discs. This produces similar symptoms of pain, numbness and pins/needles but generally, the symptoms gradually appear and get worse with time.
Hopefully this helps you have a better understanding of whats going on in your back.