The spinal vertebrae are separated by flexible discs of shock-absorbing cartilage. These discs are made of a supple outer layer with a soft jelly-like core (nucleus). If a disc is compressed, so that part of it intrudes into the spinal canal but the outer layer has not been ruptured, it may be referred to as a “bulging” disc. This condition may or may not be painful and is extremely common.

Herniated discs are often referred to as “slipped” or “ruptured” discs. When a disc herniates, the tissue located in the center (nucleus) of the disc is forced outward. Although the disc does not actually “slip,” strong pressure on the disc may force a fragment of the nucleus to rupture the outer layer of the disc.