1. The normal appearance of the obturator shadow is described.
2. In certain types of hip pathology the obturator shadow becomes obscured, or it becomes widened with a more curved border. This is called a positive obturator sign.
3. The greatest value of this sign is in the early roentgenographic diagnosis of septic hip disease.
4. It is of some importance in the early diagnosis of tuberculosis of the hip.
5. It is not present in fractures about the hip, osteochondritis, and other pathological conditions of the hip.