Your spine is made up of little bones stacked on top of one another, called vertebrae. In between each vertebra there are "discs" that are filled with water. They cushion the movement that goes through your spine when you walk and move around. Discs also contain cells that have the ability to heal small tears in the disc caused by injuries and illnesses. The discs are blue in colour in this picture to the right.

As you get older, your discs start to lose some of their water content and therefore lose some of their cushioning ability. The cells that normally help to heal small tears no longer work as quickly or as effectively and so the discs start to scar. This is called degeneration of the disc and is part of the normal aging process.