The flexibility of the intervertebral discs is a requisite for spinal mobility. These discs, which serve as the spine’s "shock absorbers", have a kind of gel cushioning inside them. This gel-like nucleus (nucleus pulposus) contains water and is surrounded by a ring of tissue fibres.
This fibre ring can become brittle and cracked, so that it can no longer adequately contain the gel-like material. If the disc is overtaxed through obesity, prolonged sitting or lifting heavy objects, the nucleus pulposus may bulge outwards. A herniated disc occurs if it ruptures the fibre ring.
Pain is caused when the herniated disc exerts pressure on the nerves extending along the spinal column. The pain can often be managed with analgesics, heat treatment and exercise therapy. However, if the pain becomes unbearable, or if paralysis occurs, surgery is usually required, as there is no other way to free the pinched nerves. When necessary, the defective intervertebral disc is removed during the procedure and replaced by an implant.