Most Things Biology

Time To Read

2–3 minutes

Date Last Modified

February 6, 2026

The ischiumPosterior, lower part of the hip bone; what you sit on. is one of the three bones that form the coxal or hip bones. The iliumBroad, flaring upper portion of the hip bone; forms the “wings” of the pelvis., ischium, and pubisAnterior portion of the hip bone; meets its pair at the pubic symphysis. are all fused together to form the coxal bones.

Illustration contrasting medial and lateral views of the right coxal bone (hip bone). The medial view on the left reveals the obturator foramen. The lateral view on the right shows the acetabulum. — Right coxal bone illustration, medial and lateral views.

Ischial tuberosity
Ischial spineProminent ridge on the posterior scapula dividing it into supraspinous and infraspinous fossae.
Ischial ramus
Lesser sciatic notch
Acetabulum
Obturator foramen

Hip Bone Study Sheet

Let’s do the easy stuff first. The big hole in the hip bone is called the obturator foramenLarge oval or round hole below acetabulum; lightens bone and allows passage of nerves/vessels.. The big depression in the hip bone is what you might want to call the hip socket. It has a more complicated name: acetabulumDeep, cup-like socket on lateral side where femur head articulates; shared by all three hip bone reg. This word means vinegar cup. The acetabulum shows us that the hip bone is actually three different bones. These bones are fused together: the ilium, ischium, and the pubis or the pubic bone. These three bones come together at the acetabulum, giving it its strength.

Have you ever had to sit on the floor or a hard chair? You might have felt like your butt bone hurts. This is the ischium portion of your hip bones. Like the pubic bone, the ischium is inferiorBelow or toward the lower part of the body. to the ilium, however it is posterior instead of anteriorThe front of the body or toward the front when standing in the anatomical position.. The ischium curves around the obturator foramen. The ischial ramusNarrow bridge of bone connecting ischium to pubis; helps form obturator foramen. is on the inside of the curve. It is where the border of the ischium and pubis is located. From pictures, it can look as if the ischial tuberosityRough, thick projection that bears body weight when sitting; major hamstring attachment. is directly opposite of the ischial ramus. However, it is slightly more superiorAbove or toward the upper part of the body. on the ischium than the ramus.

I use the sciatic notches to help me determine if I am looking at the left or right bone. They also help me determine which direction is anterior. The lesser sciatic notchSmaller notch below ischial spine for tendons and nerves. is located just below the ischial spineSharp projection between the greater and lesser sciatic notches., a projection to which many pelvic floor muscles attach. Sometimes, students confuse the ischial spine with the pubic crestRidge on superior surface of pubic body; attachment for abdominal muscles.. This can be addressed by observing the greater sciatic notchLarge notch below the PIIS where the sciatic nerve passes.. There is no notch of similar size on the anterior of the hip bones.