A lot of people look at a herniated disc and a bulging disc as two in the same. This really is not very accurate although both conditions may cause some of the same painful symptoms. When a disc is herniated the gel like inner material is released through a break in the disc this is termed as a non-contained disc, while with a bulging disc there is no actual break or tear in the discs wall but the inner material begins to bulge out through a weakened area of the disc. A bulging disc is an example of a contained disc.
Although a bulging disc may be located in the neck or back it is most common in the Lumbar region of the spine. The threat of disc problems may increase in persons who have been victim of a back injury or have made poor lifestyle choices. Age will often play influence on disc problems as well.
When a disc is bulging this is most not likely where the pain is being felt. To understand this lets look more closely at what a bulging disc is. The disc is a unit that is made up of a tough fibrous material (anulus fibrosus ) composing the outer layer. The inside of this disc is filled with a gel-like material called the nucleus pulposus. As your disc begins to lose water (going down from 85% to 65%) it is like letting air out of a tire, the sides begin to bulge. This can either cure itself as the annulus tightens up with time, or as the joints in your spine enlarge and add more stability. Most of the time these bulging discs are treatable by exercise (Lumbar Stabilization or aerobics) and/or anti-inflammatories (ASA, Ibuprofen, or Aleve), and learning not to over stress these bulging discs. Usually this can get to a pain-free situation. Occasionally a disc bulge can get so big that it squeezes the nerves and denies them nutrition (blood supply), and causes continuing leg and posterior thigh pain. This condition is called Central Disc Syndrome. Even still, this often gets better with exercise and medications. Studies have shown that if you smoke, the chances of getting better are much lower.
With all of these terms being thrown around what is a Slipped Disc? A ruptured or herniated disc can be referred to as a slipped disc. Although the term slipped disc is used, technically the disc does not actually slip. Each of these discs act as shock absorbers between two vertebrae that are supported by a system of ligaments that help to hold the spinal structure together.
Ok, so we know why a contained disc such as a bulging disc will sometimes cause pain and discomfort, why does herniated disc cause pain? The inside of the disc, the gel-like material, contains a chemical that irritates nerves causing them to swell. Once the chemical has caused the nerves to swell, the remenants of this chemical stay around and continue to press on the swollen and irritated nerves causing the painfull symptoms. To complicate matters, sometimes fragments from the anulus break away from the parent disc and drift into the spinal canal. These free fragments may travel in the spinal canal.