A disc herniation is when a small area of a disc bulges outwards. Unlike a disc bulge, which is broad and involves a large circumference of the disc, a herniation only involves a quarter of the disc circumference. Normally, whether there is a disc herniation or bulge, the margins of an intervertebral disc should not stay beyond the bone edges; they should return back to their normal position when the spine becomes relaxed. It is normal for a disc to ‘bulge’ with certain movements. However, when a disc herniates, a specific small area of the entire disc is bulging.