Hip Bone Anatomy: Complete Guide with Parts, Names & Diagram

Overview of Hip Bone Anatomy

The hip bone, or os coxae, is a large, irregular bone that forms the base of the lower limb. The main functions of the hip bone are to support the body’s weight when standing and provide a base for leg movement. It connects to the spine at the sacroiliac joint and the leg at the hip joint. Hip bone anatomy comprises three parts that fuse during the teenage years: the ilium, ischium, and pubis.

Ilium: The broad, upper part of the pelvis.
Ischium: The part of the hip bone you sit on.
Pubis: The lower, front part of the pelvis.

The acetabulum is a socket on the side of the hip where the head of the thigh bone (femur) fits in, allowing leg movement. It is formed by the three parts of the hip bone anatomy. It is separated by cartilage until the ages of 15–17 when they fuse. The hip also contains important nerves and blood vessels for movement and feeling. The femoral nerve is at the front of the thigh, the sciatic nerve runs along the back, and the smaller obturator nerve is deeper. The femoral artery, one of the body’s main arteries, can be felt at the front of the upper thigh.

Detailed Hip Bone Anatomy Diagram

Hip Bone Anatomy, Parts, Names & Diagram

Hip Bones Anatomy

Ilium
Ischium
Pubis
Acetabulum

Hip Bone Anatomy: Parts & Functions

Ilium

The ilium is a key part of the pelvic bone, comprising two main sections: the body and the wing. Together with the ischium and pubis, the ilium forms the pelvis. Where these bones join, the connections are faint and barely visible.

Body of Ilium

The body of the ilium makes up less than 40% of the acetabulum, which is the socket where the thigh bone (femur) fits. It also helps shape part of the acetabular fossa.

Inside, the body lines part of the lesser pelvis and provides an attachment point for some obturator internus muscle fibers.

Wing

The wing, also known as the ala, is the wide, flat part that forms the sides of the greater pelvis. It has an outer and inner surface, a crest, and front and back edges.

These features shape the ilium and offer important attachment points for muscles and ligaments, helping with posture and movement.

The ilium also has several important landmarks, including:

Iliac crest – It is the upper edge of the ilium, the largest bone in the pelvis.
Anterior superior iliac spine – A prominent bony projection is known as the anterior superior iliac spine at the front of the iliac crest.
Anterior inferior iliac spine – Just below the anterior superior iliac spine, we can see the anterior inferior iliac spine extends downward.
Posterior superior iliac spine – On the back side of the ilium, the posterior superior iliac spine marks the rear boundary of the iliac crest.
Posterior inferior iliac spine – Positioned below the posterior superior iliac spine, adjacent to a roughened surface called the auricular surface, which connects with the sacrum.
Iliac fossa – It is a smooth, concave region on the inner surface of the upper ilium, where muscles attach.
Greater sciatic notch – The greater sciatic notch is near the lower rear of the ilium, with a large U-shaped indentation. It allows the sciatic nerve and other structures to pass from the pelvis to the lower limbs.

Ischium

The ischium is a key part of the pelvis, playing a major role in both movement and supporting the body weight. It has three main sections:

Body

The main part of the ischium features a bump called the ischial spine, where a muscle called the superior gemellus attaches. Below this is a curved area known as the lesser sciatic notch.

Further down is the ischial tuberosity, a rough surface that supports your body when sitting, especially on hard surfaces. It is also where the hamstring muscles and the inferior gemellus muscle begin.

Superior Ramus

This section is where muscles like the internal and external obturators attach, which help rotate the thigh.

Inferior Ramus

At the front, the inferior ramus connects to the pubic bone. It provides attachment points for muscles such as the adductor magnus and gracilis, essential for leg movement.

The ramus of the ischium features key bony landmarks:

Ischial tuberosity – A prominent bony structure located at the lower part of the ramus, just below the lesser sciatic notch. It is an attachment point for muscles and bears the body’s weight when sitting.
Ischial spine – A sharp bony projection positioned between the greater and lesser sciatic notches, playing a role in ligament attachment and serving as a boundary for these notches.
Lesser sciatic notch – A small curved indentation between the ischial spine and the ischial tuberosity forms a passageway for nerves and vessels.
Greater sciatic notch – A larger, curved indentation between the posterior inferior iliac and the ischial spine, through which the sciatic nerve exits the pelvis.

Each feature contributes to the pelvis’s structural and functional integrity, supporting movement and protecting neurovascular pathways.

Pubis

In vertebrates, the pubis, or pubic bone, forms the lower front part of the hip on each side. It is the most forward-facing of the three bones that make up the hip, with each pubic bone having three main parts: the body, the superior ramus, and the inferior ramus.

Body of the Pubis

The body is the central, flat, and sturdy part of the pubic bone. It connects with the opposite pubic bone at the pubic symphysis, a joint at the body’s center.

The body’s top edge is called the pubic crest, which ends in a small bump known as the pubic tubercle. The body of the pubis has three surfaces: one facing forward (anterior), one facing backward (posterior), and one facing inward (medial).

Superior Pubic Ramus

The superior pubic ramus is the upper portion of the pubis. It forms the top boundary of the obturator foramen, a large hole in the pelvis.

The superior pubic ramus extends from the body of the pubis to the other side. It is divided into a flat inner section and a narrower outer section.

Inferior Pubic Ramus

The inferior pubic ramus is the lower branch of the pubis. It extends downward and outward, becoming thinner as it goes, and connects with the ischium, another bone in the pelvis, below the obturator foramen.

The obturator foramen lies between the superior and inferior pubic rami, and the two pubic bones meet at the pubic symphysis, allowing them to join at the middle of the pelvis.

Acetabulum

The acetabulum, also known as the cotyloid cavity, is a deep, curved surface on the pelvis that forms part of the hip joint. It is where the head of the femur fits, creating the ball-and-socket structure of the hip. Three bones of the hip—ischium, ilium, and pubis—merge to shape the acetabulum.

The ischium forms over two-fifths of the acetabulum, providing support along the lower and side areas. The ilium contributes slightly less than two-fifths to the upper portion. At the same time, the pubis, located near the center, forms the remaining part.

Lunate Surface

It is a crescent-shaped, curved area of the acetabulum.
It is the primary surface where the head of the femur connects to form the hip joint.
Provides smooth articulation for the ball-and-socket joint movement.

Acetabular Notch

Located at the lower part of the acetabulum.
It acts as a gap in the rim of the acetabulum, allowing passage for blood vessels and ligaments.
It continues with the acetabular fossa, helping support joint stability.

Acetabular Fossa

A circular depression at the bottom of the acetabular cavity.
It does not directly articulate with the femur but provides space for ligaments and the joint capsule.
It is important for distributing forces within the hip joint.

Hip Bone Anatomy – Complete Guide with Parts, Names, Functions & Diagram