Hip bone Hip bone The hip bone (os coxa, innominate bone, pelvic bone or coxal bone) is a large flat bone, constricted in the center and expanded above and below. In some vertebrates (including humans before puberty) it is composed of three parts: the ilium, ischium, and the pubis. The two hip bones join at the pubic symphysis and together with the sacrum and coccyx (the pelvic part of the spine) comprise the skeletal component of the pelvis – the pelvic girdle which surrounds the pelvic cavity. They are connected to the sacrum, which is part of the axial skeleton, at the
Sacrum the direction of rotation of the superior portion of the sacrum opposite the side of the superior axis pole, and the last letter pertains to the pole. English "sacrum" was introduced as a technical term in anatomy in the mid-18th century, as a shortening of the Late Latin name "os sacrum" "sacred bone", itself a translation of Greek ἱερόν ὀστέον, the term found in the writings of Galen. Prior to the adoption of "sacrum", the bone was also called "holy bone" in English, paralleling German "heiliges Bein" or "Heiligenbein" (alongside "Kreuzbein") and Dutch "heiligbeen". The origin of Galen's term is