There are many causes of low back pain. Workers compensation cases come in two types: immediate traumatic injury or wear and tear over time. At McCormick Law Office we handle both types of causation every day. The wear and tear type is called degeneration. Over time, the normal process of aging can result in degenerative changes in all parts of the spine. Injuries to the spine, such as a fracture or injury to the disc, can make the changes happen even faster. The intervertebral disc, the jelly doughnut shock absorber, changes over time. At first, the disc is spongy and firm. The nucleus in the center of the disc contains a great deal of water. This gives the disc its ability to absorb shock and protect the spine from heavy and repeated forces.
The first change that occurs is that the annulus around the nucleus weakens and begins to develop small cracks and tears. The body tries to heal the cracks with scar tissue. But scar tissue is not as strong as the tissue it replaces. The torn annulus can be a source of pain for two reasons. First, there are pain sensors in the outer rim of the annulus. They signal a painful response when the tear reaches the outer edge of the annulus. Second, like injuries to other tissues in the body, a tear in the annulus can cause pain due to inflammation.
With time, the disc begins to lose water, causing it to lose some of its fullness and height. As a result, the vertebrae begin to move closer together. As the disc continues to degenerate, the space between the vertebrae shrinks. This compresses the facet joints along the back of the spinal column and this may lead to arthritis in the facet joints.
These degenerative changes in the disc, facet joints, and ligaments cause the spinal segment to become loose and unstable. The extra movement causes even more wear and tear on the spine. As a result, more and larger tears occur in the annulus.
Finally, and this may be the straw that breaks the camel’s back, a person is lifting something and the nucleus pushes through the torn annulus and into the spinal canal. This is called a herniated or ruptured disc. If you remember this happening in a single incident, it is a traumatic injury. The disc material that squeezes out can press against the spinal nerves. The disc also emits enzymes and chemicals that produce inflammation. The combination of pressure on the nerves and inflammation caused by the chemicals released from the disc cause low back pain.