The disc is the shock absorber between vertebrae. It is composed by an outer layer called the annulus fibrosis which is a crisscrossed layer of strands of very strong collagenous fibers. The job of this layer is to support and contain the inner cushioning nucleus pulposus, think of it like the jelly inside a jelly filled donut.
The outer and inner layers become dehydrated and less resilient to stress as we age or with compromised circulation to the area. Repetitive motion can cause fibers in the outer layer to stretch or fail. Since the inner layer is under a lot of pressure it will follow the path of least resistance. In the case of a bulge it will pooch out to the side, this creates even more pressure and stress on the supporting fibers. If the fibers fail the disc can escape into the surrounding tissues creating a disc herniation, think about stepping on the jelly donut. The inner disc is chemically irritating to the surrounding tissue, much like stomach acid that is fine in the stomach but not good in the upper part of the digestive tract. When the disc escapes containment a huge inflammatory response occurs. The body eventually encapsulates the herniation putting a protective wall around it, this can take a few weeks and the chemically activated inflammatory response can diminish.
If you are lucky and the bulge is not located close to anything important, complaints can disappear. If, however, the bulge is near a moving joint it can be a source of aggravation, like a rock in your shoe. In the worst case scenario the bulge puts direct pressure on the spinal cord or spinal nerve. Pain, numbness, pins and needles can be present in distant parts of the extremities with minimal pressure but with excessive pressure the nerve looses its ability to communicate with distant muscles, this is called a radiculopathy. Eventually with sustained excessive pressure the nerve can die resulting in permanent damage (See your doctor if you have severe pain and loose the function in specific muscles – sometimes early surgical intervention is appropriate and can restore full function.)
While this seems a little scary, in reality a full third of the population is walking around with a disc herniation yet has had no complaints of pain or limited function. By the age of 80, 80% of the population has a disc herniation visible on MRI. Given this knowledge do not assume that because you have a bulge or herniation that you won’t be able to live a life without pain or limitation. Fascial Counterstrain is an effective intervention.