Why do we have pain?

There are fibers along the annulus fibrosis.  Also, there are nucleus fibers coming off the nerve root, which are pain fibers.  A disc that degenerates will have fissures that cause pain, by irritating the nerve roots. An annular tear causes the nucleus to come out so as it bulges towards the fibers, it will cause the person to feel pain. Disc herniation can occur laterally by compressing the nerve root before coming out the neural foramen causing pain down the leg, which is called sciatica. Depending on the nerve it can be upper leg, lower leg, or the whole leg.