Most of the prison stabbings are included in violent crimes stats. I guess some rapes may not be, though. Rape in prisons is surpassing non-prison rape (which is almost nonexistent) but it's not routine either - 10x higher rate per person-year is still a pretty low rate (needless to say: we the public should be willing to pay a pretty high price to stop a single violent rape - say, $50k)