The “hip bone” is a familiar term, often used to describe a prominent part of our lower body. Though commonly thought of as a single structure, this area represents a complex and important component of the human skeleton. It plays a central role in supporting the upper body and enabling a wide range of movements.
Locating the Hip Region
To locate your hip region, place your hands on your waist, just above your pants line. Slide your hands downwards and slightly inwards. You will feel a curved, bony ridge on each side. This prominent top edge is the iliac crest, part of what is commonly referred to as the hip bone.
The iliac crest forms the upper, outer boundary of the hip area and can be easily felt along its entire length. This bony landmark marks the upper border of the ilium, one of the bones that make up the hip structure. It extends from a point near the front of your body (anterior superior iliac spine) to one near your lower back (posterior superior iliac spine).
The Pelvic Girdle: More Than One Bone
The common idea of a single “hip bone” is a simplification. The structure referred to as the hip bone is actually a complex bony ring called the pelvic girdle. This girdle is formed by two large, curved hip bones, joined at the front and connected to the sacrum at the back. The sacrum is a triangular bone at the base of the spine, and together with the hip bones, it forms the entire pelvis.
Each of the two hip bones, also known as a coxal bone, is formed from three separate bones that fuse together during development: the ilium, the ischium, and the pubis. The ilium is the largest, forming the broad, upper part, while the ischium is located posterolaterally, and the pubis forms the anterior portion. These three bones meet and fuse at a deep, cup-shaped socket called the acetabulum, where the thigh bone (femur) connects to form the hip joint. This fusion begins during puberty and is complete by the early to mid-twenties.
Essential Functions of the Hip Bones
The pelvic girdle performs several essential functions. It acts as a stable base, supporting the weight of the upper body. This weight is then transferred through the pelvic girdle to the lower limbs, both when standing and during movement.
The hip bones also provide numerous attachment points for muscles of the trunk and lower limbs. These muscles enable a wide range of movements, including walking, running, and jumping, making the pelvic girdle a key component for locomotion. The structure’s stability provides a strong foundation for the upper body.
The pelvic girdle creates a protective enclosure for various organs within the pelvic cavity. These include parts of the digestive system, such as the rectum, as well as the urinary bladder and reproductive organs. The robust, ring-like structure of the pelvic girdle safeguards these soft tissues from external forces.