The obturator sign is an indicator of irritation to the obturator internus muscle.
The technique is carried out on each leg in succession. First the patient lies on his back with the right hip flexed at 90 degrees. The examiner then holds the patient's right ankle in his right hand. With his left hand, the examiner rotates the hip by pulling the right knee to and away from the patient's body.
In the clinical context, it is performed when acute appendicitis is suspected. In this condition, the appendix becomes inflamed and enlarged. The appendix may come into physical contact with the obturator internus muscle, which will be stretched by this physical examination maneuver. This causes pain and is an evidence in support of an inflamed appendix.
The principles of the obturator sign in the diagnosis of appendicitis are similar to that of the psoas sign.