my mother is experiencing a lot of low back pain extending to her hips. It seemed to happen sharply last week after she sat down ( fell down) hard onto the toilet seat. Xrays only indicate severe arthritis, but her brother died from bone cancer experiencing a lot of pain before dying so she is concerned. She is 93, weighs 175, has a pacemaker, has survived early stage colon cancer, is otherwise healthy, lives alone and has been able to care for herself until now. Can bone cancer manifest itself so quickly?