Why do discs herniate?

[minolfa]

I checked and found nothing "evidence based"...
Just out of curiosity I found that "muscone" is a promising agent
for treating intervertebral disc degeneration...also, Okuma et al.
showed that oral administration of CPA -926 (an esculetin prodrug)can prevent or delay the onset of disc-height loss....

I do not trust stem cells because I have heard they are carcinogenic.