The obturator internus is a fan-shaped muscle located in the pelvis. The muscle originates partly from the inner surface of the obturator membrane that covers most of the obturator foramen, an opening between two sections of the hip bone. The rest of the muscle originates along the bony back edge of the foramen. The other end of the muscle narrows to a tendon that inserts into the middle of the bony surface of the greater trochanter of the femur, which is the bulbous portion of the upper thighbone. The internal pudendal artery and the two gluteal arteries (superior and inferior) provide blood supply for the muscle.
Its primary function is to help move the thigh away from the center of the body by rotating it in a sideways direction. When the thigh is flexed, it assists other muscles in moving the thigh outward, away from the midline of the body. It also helps to stabilize the hip joint.