Pelvis

What is your pelvis?

Your pelvis is the seat of your axial skeleton (the central core of your skeletal system). It holds up your trunk and connects it with your legs below. Your pelvic bones form a sort of basin at the base of your spine, with an opening in the middle. These are the bones of your hips, buttocks and pubic area.

Sometimes, healthcare providers use “pelvis” to refer to the whole pelvic region of your body (between your abdomen and thighs). Pelvic pain usually involves the organs inside this space. These include your urinary system, reproductive system, rectum and anus. A pelvic exam generally examines these organs.

What does your pelvis do in your body?

Your pelvic bones support the weight of your upper body, together with the muscles of your pelvic floor. Your pelvic cavity, the space between your pelvis and abdomen, holds your urinary and reproductive organs. The opening in your pelvis serves as the birth canal in people assigned female at birth (AFAB).

What are the pelvis bones?

Five separate bones combine to form your bony pelvis. Your pelvic bones include your:

• Sacrum. Your sacrum is a spade-shaped bone at the base of your spine. It forms when the last five vertebrae of your spine fuse together, a process that takes until puberty to complete.
• Coccyx. Your coccyx is your tailbone, the small, final bone at the tip of your spine and sacrum. Healthcare providers sometimes refer to your sacrum and coccyx together as your pelvic spine.
• Ilium. Your ilium, ischium and pubis make up your pelvic girdle, the bones that encircle your pelvic spine. These bones also are separate in childhood and fuse together during puberty. Your ilium is the largest of them: a broad, concave bone that wraps around the sides of your hips.
• Ischium. Your ischium (singular) or ischia (plural) are your “sit bones.” The two “U”-shaped bones hang from the base of your pelvic girdle and form the bony part of your buttocks.
• Pubis. Your pubis, or pubic bone, is the smallest bone on each side of your pelvis. Your two pubic bones meet in the front and center of your pelvis at a joint called your pubic symphysis.

What are the important joints in your pelvis?

A joint is where any two bones meet. In your pelvis, several small joints between the vertebrae of your pelvic spine help your spine move. There are also several joints that connect the bones of your pelvic girdle to each other and the rest of your body. Cartilage and ligaments hold them together.

Joints in your pelvic spine include your:

• Sacrococcygeal joint. This joint connects your sacrum to your coccyx below.
• Lumbosacral joints. These joints connect your lumbar spine with your sacrum below.

Joints in your pelvic girdle include your:

• Pubic symphysis. This is the joint between your two pubic bones in the front of your pelvis.
• Sacroiliac joints. These are the joints that connect each ilium bone to your sacrum.
• Hip joint. This joint connects your thigh bone to your ilium at a socket called the acetabulum.

What are the four types of pelvis shapes?

Historically, healthcare providers classified pelvic shapes into four basic types. Today, providers recognize that pelvic shapes exist on a spectrum rather than falling into only four types. But the types still exist as a reference point. They mainly differ by the shape of the pelvic opening at the top (inlet).

• Android: The android pelvis is roughly heart-shaped, with a conical or wedge-shaped opening. It’s typically wider at the top of the opening (inlet) and narrower towards the bottom (outlet).
• Anthropoid: The anthropoid pelvis is narrower than others, deeper than wide, with an oval-shaped opening. With an anthropoid pelvis, you may have longer butt muscles than average.
• Gynecoid: The gynecoid pelvis is rounder than others, with wide hips and a wide, round opening. Healthcare providers tend to associate this shape with the easiest vaginal delivery.
• Platypelloid: The platypelloid pelvis is the least common of the four types. It’s wide and shallow, with pronounced hips and a flat front and back. The shape resembles a bean more than a heart.

What are the differences in male pelvis anatomy vs. female pelvis anatomy?

Whether you were assigned female or male at birth, your pelvis will continue to grow and change through puberty. By adulthood, your pelvic anatomy will differ in certain ways by the reproductive organs you have. These differences have evolved together with our different reproductive systems.

If you have a female reproductive system, your pelvis anatomy is optimized for childbirth. This means:

• It’s broader and shallower, with a larger opening (inlet).
• Your ischia (butt bones) are farther apart, making the outlet wider.
• Your pubic arch (convergence of your pubic bones) is wider.
• Your acetabula (hip sockets) are farther apart and angled inward.
• Your sacrum is shorter and wider.
• Your coccyx is moveable.

On the other hand, if you have a male reproductive system, your pelvis doesn’t have to accommodate childbirth. So, your pelvis anatomy is optimized for walking and running on two feet instead. This means:

• It’s taller, narrower and more compact.
• It narrows from top to bottom.
• Your pubic arch is a narrower angle (more “V” shaped).
• Your acetabula (hip sockets) are closer together and angled outward.
• Your sacrum is longer, narrower and straighter.
• Your coccyx is angled inward and doesn’t move.

What types of health conditions can affect your pelvis?

The bones and joints of your pelvis are subject to the same injuries as others in your body, including fractures, dislocations and repetitive strain injuries. You can get arthritis in your pelvic joints. Pregnancy and childbirth can also cause temporary pelvic joint pain. Some specific pelvic conditions include:

• Cephalopelvic disproportion.
• Coccydynia.
• Pelvic fractures.
• Sacroiliitis.
• Spondyloarthritis.
• Symphysis pubis dysfunction.

Conditions related to connective tissues within your pelvis include:

• Ischial bursitis.
• Pelvic congestion syndrome.
• Piriformis syndrome.
• Pudendal neuralgia.
• Round ligament pain.

What types of tests can check the health of your pelvis?

Exams of your pelvis include:

• Pelvic physical exam.
• Pelvic ultrasound.
• Pelvis X-ray.