Obturator foramen

The obturator foramen, a large opening in the pelvic or hip bone, lies just below the acetabulum. It is bounded anteriorly by the pubic bone and posteriorly by the thick ischium. The ischiopubic ramus forms its lower margin, while the superior ramus of the pubis and the body of the ischium form its upper margin.

Covering the margins of the obturator foramen, except for the obturator groove, is the obturator membrane. The groove is located on the underside of the superior ramus of the pubis and forms part of the upper margin of the foramen. The absence of the obturator membrane in the region of the obturator groove creates a passage known as the obturator canal. This canal allows for the passage of the obturator vessels and nerves from the pelvic region into the medial or adductor compartment of the thigh.

The inner and outer aspects of the lower pelvic wall are further covered by the obturator internus and externus muscles, which overlay the obturator foramen and membrane.