The obturator internus muscle helps move the thigh away from the center of the body by rotating it laterally. When the thigh is flexed, it assists other muscles in moving the thigh outward, away from the midline of the body. It also helps stabilize the hip joint.The muscle is supplied by a nerve that originates in the fifth lumbar and the first and second sacral nerves.

The blood supply comes from the internal pudendal artery and the two gluteal arteries: the superior and inferior.The obturator internus 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 fan-shaped 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, the bulbous portion of the upper thigh bone.