The (pelvis pl. pelvises or pelves) is the bony structure locate at the base of the spine (properly known as the caudal end). It is part of the appendicular skeleton. Each os coxae (hipbone) consists of three bones: the ilium, ischium, and the pubis. The ilium is the largest and upper most part, the ischium is the posterior-inferior (back-lower) part, and the pubis is the anterior (front) part of the hipbone. The two hipbones are joined anteriorly at the symphysis pubis and posteriorly to the sacrum. The pelvis incorporates the socket portion of the hip joint for each leg (in bipeds) or hind leg (in quadrupeds). It forms the lower limb (or hind-limb) girdle of the skeleton.