The hipbone is a large irregular flat bone located in the pelvic region.
Two hip bones, along with the sacrum and coccyx, form the bony pelvis.
It has three parts: ilium, pubis, ischium.
Early life: three bones separated by Y-shaped cartilage, later ossifies at acetabular cavity.
Acetabulum: cavity on lateral side, articulates with femur to form hip joint.
Ilium
Flat expanded part above the acetabular cavity.
Parts: two ends (upper and lower), three borders (anterior, posterior, medial), three surfaces (gluteal, iliac fossa, pelvic).
Upper End (Iliac Crest)
Elongated and expanded, highest point between third and fourth lumbar vertebrae.
Anterior superior iliac spine: a projection at the anterior end.
Posterior superior iliac spine: a projection at the posterior end.
Ventral segment: outer lip, inner lip, intermediate segment (tubercle about 5 cm behind anterior superior iliac spine).
Dorsal segment: inner and outer surface separated by a ridge.
Lower End
Smaller, forms ~2/5 of the articular surface of the acetabulum.
Borders
Anterior: from anterior superior iliac spine to acetabulum.
Posterior: from posterior superior iliac spine, continuous with posterior border of ischium, includes greater sciatic notch, ischial spine, lesser sciatic notch.
Medial: from iliac crest to iliopubic eminence, includes the arcuate line.
Surfaces
Gluteal surface: convex anteriorly, concave posteriorly, split by three lines (posterior, anterior, inferior gluteal lines).
Iliac fossa: smooth and concave, nutrient foramen present.
Sacral pelvic surface: divided into sacral and pelvic parts, includes auricular surface (resembles ear, articulates with sacrum).
Pubis
Forms the anterior part of hip bone, articulates with opposite bone forming symphysis pubis.
Parts: body, superior ramus, inferior ramus.
Body
Connects superior and inferior ramus, has three surfaces and one border (pubic crest and tubercle).
Surfaces: anterior (forms anterior wall of bony pelvis), posterior (smooth), symphyseal (rough, oval, forms cartilaginous joint).
Pubic crest: blunt upper border.
Pubic tubercle: crossed by spermatic cord in males, round ligament of the uterus in females.
Superior Ramus
Arises from lateral angle of body, passes above obturator foramen, unites with ilium.
Borders and surfaces: obturator crest, pectineal line, pelvic surface.
Inferior Ramus
Extends backwards, unites with ischium ramus.
Borders and surfaces: anterior and posterior surfaces, medial and lateral borders.
Ischium
Forms posterior and lower part of hip bone, contributes to acetabulum.
Parts: body and ramus.
Body
Upper end: fuses with ilium and pubis, part of acetabular cavity.
Lower end: forms ischial tuberosity (divided into areas).