Pelvis is a ring structure formed by sacrum, coccyx, and the innominate bones (ilium, ischium and pubis). The innominate bones articulate posteriorly with the sacrum and anteriorly through pubic symphysis (Fig. 30.1). Acetabulum is formed by fusion of these three innominate bones, and in paediatric age group, they are connected by the triradiate cartilage. The pelvis contains blood vessels, nerves, urogenital organs, and the rectum. True pelvis is the space below the pelvic brim, and false pelvis is the space above pelvic brim (Fig. 30.2).