 Osteonecrosis can affect any bone, but the hips, knees and jaws are most often involved.Pain can often be severe, especially if teeth and/or a branch of the trigeminal nerve is involved, but many patients do not experience pain, at least in the earlier stages.When severe facial pain is purported to be caused by osteonecrosis, the term NICO, for neuralgia-inducing cavitational osteonecrosis, is sometimes used, but this is controversial and far from completely understood.