Pelvic Girdle

The pelvic girdle, also known as the bony pelvis, is a ring-like structure of bones located at the lower end of the trunk. It connects the vertebral column to the lower limbs and supports the weight of the upper body when sitting or standing. Composed of paired hip bones (ossa coxae), the sacrum, and the coccyx, the pelvic girdle plays essential roles in locomotion, posture, and protection of internal pelvic organs.

Structure

The pelvic girdle consists of three main components on each side: the ilium, ischium, and pubis. These bones fuse in adulthood to form a single os coxae on each side. The sacrum and coccyx form the posterior part of the girdle.

1. Ilium

• The broad, flaring part of the hip bone
• Forms the superior portion of the acetabulum
• Notable landmarks: iliac crest, anterior superior iliac spine (ASIS), posterior superior iliac spine (PSIS)

2. Ischium

• Forms the posteroinferior part of the hip bone
• Contains the ischial tuberosity — a major weight-bearing point when sitting

3. Pubis

• The anteroinferior part of the hip bone
• Two pubic bones meet at the midline at the pubic symphysis
• Forms the anterior portion of the acetabulum

4. Sacrum

• Triangular bone formed by the fusion of five sacral vertebrae
• Connects the spine to the pelvic girdle at the sacroiliac joints

5. Coccyx

• Small, tail-like bone formed by fusion of 3–5 rudimentary vertebrae
• Serves as an attachment for ligaments and muscles of the pelvic floor

Location

The pelvic girdle is located at the junction of the trunk and lower limbs. It forms the inferior part of the axial skeleton and articulates laterally with the femurs at the hip joints. Posteriorly, it connects with the vertebral column at the sacroiliac joints, and anteriorly, the pubic bones join at the pubic symphysis.

Function

• Support: Bears the weight of the upper body and transfers it to the lower limbs via the hip joints
• Protection: Encases pelvic organs such as the bladder, rectum, and reproductive organs
• Attachment Site: Provides surface for muscle and ligament attachment — essential for posture and movement
• Childbirth: In females, the pelvic girdle forms the birth canal, making its shape and size clinically significant

Clinical Significance

• Pelvic Fractures: High-energy trauma can lead to complex fractures affecting multiple pelvic components; these are often life-threatening due to associated vascular injuries
• Sacroiliac Joint Dysfunction: Can result in lower back or pelvic pain and may be caused by inflammation, degeneration, or instability of the sacroiliac joint
• Pelvic Asymmetry: Variations in bone structure or leg length discrepancies can affect gait and posture
• Obstetric Pelvimetry: Evaluation of pelvic dimensions in females is critical for assessing potential complications during vaginal delivery