The os coxa, also known as the hip bone, is an irregularly shaped, bilateral bone of the bony pelvis. It's also referred to as the innominate bone, pelvic bone, or coxal bone.
In simpler terms, it's one of the two bones that make up the pelvis. Each hip bone is formed by the fusion of three bones:
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Ilium: The largest and uppermost bone of the os coxa. It forms the superior part of the acetabulum (the hip socket).
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Ischium: The lower and posterior bone of the os coxa. It also contributes to the acetabulum.
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Pubis: The anterior and inferior bone of the os coxa. It connects to the other pubis bone at the pubic symphysis.
These three bones are separate in childhood, but they fuse together during adolescence to form a single bone – the os coxa. This bone articulates with the sacrum at the sacroiliac joint, forming the posterior part of the pelvis. It also articulates with the femur at the acetabulum (hip socket), forming the hip joint.
Therefore, the os coxa is a crucial bone involved in weight-bearing, locomotion, and protecting pelvic organs.
