parts of the pelvis

3 min read 10-03-2025

The pelvis is a complex bony structure located at the base of the spine. It plays a crucial role in supporting the upper body, facilitating movement, and protecting vital organs. This article provides a detailed look at the different parts of the pelvis, their functions, and common conditions that affect them.

The Three Main Bones of the Pelvis

The pelvis is primarily formed by three bones: the two hip bones (also known as innominate bones or coxal bones) and the sacrum. Let's explore each in detail:

1. Hip Bones (Innominate Bones or Coxal Bones)

Each hip bone is actually formed by the fusion of three separate bones during development: the ilium, ischium, and pubis. This fusion typically occurs by the time of puberty.

Ilium: This is the largest of the three bones, forming the upper, wing-like portion of the hip bone. Its superior portion, the iliac crest, is easily palpable on the sides of the hip. The ilium provides significant attachment points for many important muscles.
Ischium: This is the lower, posterior portion of the hip bone. It's the bone you sit on. The ischial tuberosity, the roughened part of the ischium, bears the weight of the body when seated.
Pubis: Located at the front of the hip bone, the pubis contributes to the formation of the pubic symphysis, a cartilaginous joint that connects the two hip bones. The pubic bones also provide attachment points for muscles involved in hip and abdominal movements.

2. Sacrum

The sacrum is a triangular bone located at the base of the spine. It's formed by the fusion of five sacral vertebrae. The sacrum connects the pelvis to the spine and plays a vital role in weight transfer and stability. Its articulation with the hip bones forms the sacroiliac joints.

3. Coccyx

Often overlooked, the coccyx, or tailbone, is a small, triangular bone located at the very bottom of the spine. It's formed by the fusion of three to five coccygeal vertebrae. While relatively insignificant in weight-bearing, the coccyx plays a role in muscle attachments and provides some stability to the pelvic floor.

Pelvic Joints and Ligaments

The bones of the pelvis are interconnected by several important joints and ligaments that contribute to stability and flexibility:

Sacroiliac (SI) Joints: These are strong, slightly movable joints that connect the sacrum to each hip bone. They are crucial for transmitting weight from the upper body to the legs.
Pubic Symphysis: This is a cartilaginous joint that connects the pubic bones of the two hip bones. It allows for a small amount of movement, particularly during pregnancy and childbirth.
Pelvic Ligaments: Numerous strong ligaments reinforce the pelvic joints and provide stability. These include the sacroiliac ligaments, the iliolumbar ligaments, and the pubic ligaments.

Pelvic Floor Muscles

The pelvic floor is a group of muscles that form the base of the pelvis. These muscles support the pelvic organs (bladder, uterus, rectum), control urination and defecation, and play a significant role in sexual function. Weakness in the pelvic floor can lead to conditions such as urinary incontinence and prolapse of pelvic organs.

Common Conditions Affecting the Pelvis

Several conditions can affect the pelvis, including:

Pelvic fractures: These can occur due to high-impact trauma.
Sacroiliac joint dysfunction: This involves pain and dysfunction in the sacroiliac joints.
Pelvic inflammatory disease (PID): This is an infection of the female reproductive organs.
Osteoarthritis of the pelvic joints: This is a degenerative joint disease that can cause pain and stiffness.
Pelvic organ prolapse: This is a condition in which the pelvic organs bulge down into the vagina.

Conclusion

The pelvis is a remarkably intricate structure crucial for locomotion, stability, and the protection of vital organs. Understanding its various parts, their interactions, and the potential conditions that can affect it is important for maintaining overall health and well-being. This information serves as a general overview; consulting with a medical professional is crucial for any concerns regarding pelvic health.