innominata

Innomina a.plural form innominata refers to the hip bones of the pelvis, also called os coxae or innominate bones. Each innominate bone is formed by the fusion of three embryologic elements: the ilium, ischium, and pubis. In humans, two innominata form the pelvic girdle and, together with the sacrum and coccyx, constitute the bony pelvis.

The three components of the innominate bone fuse during adolescence, typically by the late teens. The ilium is the wide, superior part bearing the iliac crest and greater sciatic notch; the ischium forms the posterior and inferior portion; the pubis constitutes the anterior inferior portion. The acetabulum, a deep socket formed at the junction of the three elements, receives the femoral head. The obturator foramen is largely bounded by the pubis and ischium. The iliac crest and anterior superior iliac spine are important surface landmarks.

Each innominate bone articulates with the sacrum at the sacroiliac joint and with the other innominate bone at the pubic symphysis; together these joints, along with the sacrum and coccyx, form the bony pelvis. The pelvis functions to support and transfer upper body weight to the lower limbs, protect pelvic organs, and provide attachment points for muscles of the hip, abdomen, and pelvis.

Etymology: the term innominate derives from Latin innominatus, meaning nameless or unidentified; the plural innominata is used to refer to the pair of hip bones.