Bones of Pelvis

Hip Bone

The Hip Bone is a large unusual flat bone in the region of hip. The hip bone is created by the fusion of 3 primary bones- the ilium, the ischium, and the pubis.
The hip bone presents upper and lower increased parts and a middle constricted part which takes a cup shaped hollow (acetabulum) on the outer aspect. The upper enlarged part is named ilium.
The lower enlarged part presents an oval or triangular foramen referred to as obturator foramen. The part anteromedial to this foramen is known as pubis, and the part posteroinferior to it’s named ischium.

Coccyx

Coccyx or tailbone is a small, triangular bone created by the fusion of 4 vestigial coccygeal vertebrae, which increasingly reduce in size from above downward. At the level of the upper border of the pubic symphysis, the tip of coccyx is located. In the natal cleft, the coccyx can be palpated.
It’s created by the upper surface of the body of the very first coccygeal vertebra and articulates with the apex of sacrum to create a cartilaginous sacrococcygeal joint.
Pelvic Girdle
The pelvic girdle consists of two coxal bones, or hip bones, that support the attachment of the lower limbs. The coxal bones articulate with the sacrum posteriorly and with each other anteriorly to form an almost rigid, bony pelvis (plural, pelves).

Pubic Symphysis

Every one of the joint’s surfaces is enveloped by hyaline cartilage and is connected throughout the midline to surrounding surfaces by fibrocartilage. The pubic symphysis is located anteriorly in between the surrounding surfaces of the pubic bones.
Functionally, the pubic symphysis is referred to as a secondary cartilaginous (fibrocartilage) joint and biomechanically, while starting as a synchondrosis, pubic symphysis becomes a nonsynovial amphi-arthrodial joint. The pubic symphysis joint includes two pubic bones (each including a pubic body and superior and inferior rami) and a stepping in fibrocartilaginous disc.

Sacrum

Sacrum is termed as a large flattened triangular/ wedge shaped bone created by the fusion of 5 sacral vertebrae. The sacrum articulates on either side with all the hip bone to create the sacroiliac joint. Sacrum has the following functions:
• Sacrum Creates posterior part of the bony pelvis.
• Supports the vertebral column.
• Conducts the weight of the body to the pelvic girdle via the sacroiliac joints.

The base of the sacrum is directed upward and forward. It’s created by the superior surface of the very first sacral vertebra. The sacrum of the base is split into 3 parts: median part and right and left lateral parts.