It can not determine broken bones, at least normally. This would be rare and only in a third world country with no x-ray machine. They order a pelvic ultrasound if you are having abnormal periods or bleeding. Pain or unusually discomfort. If they feel a mass during your pelvic exam. Enlarged uterus, or pregnancy. Cyst's on your ovary's. Bloating is common reason, especially if you are older (over 40) because it is a symptom of ovarian cancer.
If they think you have a problem in the pelvic area. It can determine broken bones, urethra tube blockage....ect