The human hip bone, or os coxae, is a complex, irregularly shaped structure formed by the fusion of three primary bones: the ilium, ischium, and pubis. This lateral view of a cadaveric specimen highlights the essential landmarks necessary for understanding pelvic biomechanics and orthopedic surgery. The hip bone serves as the mechanical link between the axial skeleton and the lower limbs, facilitating weight transfer and locomotion.
ILIAC CREST: The superior border of the ilium that forms the prominent ridge of the hip. It serves as an attachment site for various muscles, including the abdominal wall muscles and the tensor fasciae latae.
WING OF ILIUM: The large, fan-shaped upper portion of the ilium bone often referred to as the ala. It provides an extensive surface area for the origin of the gluteal muscles which are vital for hip stability.
ANTERIOR GLUTEAL LINE: A bony ridge on the lateral surface of the ilium wing. It marks the anatomical boundary between the origins of the gluteus medius and gluteus minimus muscles.
ANT. SUP. ILIAC SPINE: The anterior-most projection of the iliac crest. This landmark is easily palpable through the skin and serves as the point of origin for the sartorius muscle.
POST. SUP. ILIAC SPINE: The posterior-most projection of the iliac crest. It is often marked by a “dimple” in the overlying skin and indicates the level of the second sacral vertebra.
POSTERIOR GLUTEAL LINE: The shortest of the three gluteal lines, located near the posterior border of the ilium. It delimits the origin of the gluteus maximus muscle from the posterior surface of the bone.
POST.-INF. ILIAC SPINE: A bony projection located just below the posterior superior iliac spine. It forms the superior margin of the greater sciatic notch and serves as an attachment point for sacroiliac ligaments.
GREATER SCIATIC NOTCH: A large indentation located inferior to the posterior inferior iliac spine. It allows for the passage of the sciatic nerve and the piriformis muscle from the pelvic cavity to the gluteal region.
ISCHIAL SPINE: A pointed bony projection that separates the greater sciatic notch from the lesser sciatic notch. It serves as an important attachment point for the sacrospinous ligament.
LESSER SCIATIC NOTCH: A smaller indentation located below the ischial spine. This notch serves as a pathway for the obturator internus muscle tendon and the pudendal nerve.
BODY OF ISCHION: The thick posterior portion of the ischium that contributes to the formation of the lower-posterior part of the acetabulum. It acts as a structural foundation for the ischial tuberosity.
ISCHIAL TUBEROSITY: A large, roughened bony prominence on the inferior part of the ischium. It is the primary site of origin for the hamstring muscles and supports the body’s weight when in a seated position.
ISCHIUM RAMUS: The thin part of the ischium that extends forward and upward from the tuberosity. It fuses with the inferior pubic ramus to form the combined ischiopubic ramus.
INFERIOR PUBIC RAMUS: The lower branch of the pubis bone that joins with the ischial ramus. Together, these structures form the inferior boundary of the obturator foramen.
OBTURATOR FORAMEN: A large opening formed by the ischium and pubis bones. In a living subject, it is mostly closed by the obturator membrane, leaving only a small canal for the passage of the obturator nerves and vessels.
SUPERIOR PUBI RAMUS: The upper branch of the pubis bone that extends from the body toward the acetabulum. It forms the superior border of the obturator foramen and contributes to the acetabular construction.
ACETABULAR NOTCH: A deep gap in the inferior margin of the acetabulum rim. It is bridged by the transverse acetabular ligament, which completes the circle of the socket for the femoral head.
PUBIC BODY: The thick, medial portion of the pubis bone. It articulates with the body of the opposite pubis at the pubic symphysis, forming the front of the pelvic girdle.
ACETABULAR FOSSA: The non-articular, central deep floor of the acetabulum. It contains a fat pad and provides an attachment for the ligamentum teres, which connects the hip bone to the femur.
LUNATE SURFACE: The smooth, crescent-shaped articular surface of the acetabulum. This surface is covered with articular cartilage and is the primary area of weight-bearing articulation with the head of the femur.
ACETABULAR MARGIN: The prominent bony rim that surrounds the acetabulum. It provides stability to the hip joint and serves as an attachment site for the fibrocartilaginous labrum.
ANT.-INF. ILIAC SPINE: A bony projection located inferior to the anterior superior iliac spine. It serves as the origin for the straight head of the rectus femoris muscle and the iliofemoral ligament.
BODY OF ILIUM: The central part of the ilium bone that joins with the ischium and pubis. It forms the superior two-fifths of the acetabulum, completing the structure of the hip socket.
Functional Significance of the Pelvic Anatomy
The hip bone, anatomically known as the coxal bone, is a large, irregular bone that constitutes the primary part of the pelvic girdle. In an adult, it is a single fused unit, but it originates as three distinct elements: the ilium, ischium, and pubis. These three components meet at the acetabulum, the deep, cup-shaped socket that receives the head of the femur to form the ball-and-socket hip joint.
The lateral view of the hip bone is essential for clinical diagnosis and surgical planning. Surgeons must navigate these landmarks during procedures such as total hip arthroplasty or complex pelvic fracture fixation. Understanding the precise relationship between these structures helps in identifying critical nerve pathways and specific muscle attachment sites that are vital for postoperative recovery.
Key functions of the hip bone include:
- Providing a stable and robust base for the attachment of the powerful lower limb and trunk muscles.
- Efficiently transferring the weight of the upper body to the lower limbs during standing and locomotion.
- Protecting the internal pelvic organs, including the bladder, rectum, and reproductive tract.
- Facilitating the wide range of motion essential for activities like walking, climbing, and sitting.
The pelvic girdle itself is a marvel of biological engineering, featuring the lunate surface for weight distribution. This crescent-shaped surface is designed to handle high-pressure loads while minimizing friction through specialized hyaline cartilage. Any damage to this area, such as a labral tear or degenerative arthritis, can significantly impair a patient’s mobility and quality of life.
Mastering hip bone anatomy is fundamental for healthcare professionals ranging from physiotherapists to orthopedic surgeons. This lateral perspective illustrates how various bony landmarks serve as mechanical levers for muscle action and protective barriers for internal structures. By studying these cadaveric details, we gain a deeper appreciation for the structural integrity and functional complexity of the human skeletal system.
