Pain. Osteonecrosis causes pain and stiffness. It is most commonly found in the hip followed by the knee. See an orthopedic surgeon early, as some procedures can be used to arrest progression early in the disease process (not uniformly successful). After structural damage and mechanical malalignment have occured, arthroplasty may be necessary.
Can lose function. One can lose function of that body as it has died and hence can lose the ability to use it. So, if it occurs in the jaw, potentially eating may be a problem as if the bones are dead, teeth may fall out. If it is in the foot, common at the second metatarsal head, the person can have pain and swelling at that part of the foot which would make it difficult to walk.