Written by: Liz Paton, MSc

Pelvis Anatomy Overview

The pelvis connects the trunk of the body to the legs. It is important for weight bearing, childbirth and helps to support our organs. Take a look at our Pelvic Model to see the structure.

Motion 

The pelvis has different motions when we stand and when we walk. The pelvis can move in three planes which include the sagittal plane (motion from a side view), frontal plane (motion from the front view) and the transverse plane (motion perpendicular to the frontal plane).  

Motion of the hip includes anterior and posterior pelvic tilt which is when the pelvis rotates forwards/backwards in the sagittal plane. When one side of the pelvis sits lower than the other side of the pelvis it is known as depression or elevation of the pelvis in the frontal plane. Internal and external rotation of the pelvis occurs in the transverse plane. 

Bones  

The pelvis is made up of the pelvic spine and the pelvic girdle. The pelvic spine consists of the sacrum and the coccyx, the lowest part of the spinal column. 

The pelvic girdle is formed by three bones, the ilium, ischium and the pubis.  The ilium is the upper part of the pelvis, the ischium is the lower back part of the pelvis and the pubis is the lower front part of the pelvis. These bones are fused together which are called the innominate (not names or classified) bones. There are two innominate bones on each side of the pelvis. 

The pelvic cavity is the space within the pelvis. Within the pelvic cavity, there is a true pelvis, which is part of the pelvis and a false pelvis, which is part of the abdominal cavity. 

Joints 

Joints are the interface between two bones. The pelvis is connected by three main joints: the sacroiliac joint, the pubic symphysis and the sacrococcygeal joint. The sacroiliac joint is a synovial joint that joins the sacrum to the ilium. The pubic symphysis is a cartilaginous joint that joins the two pubic bones together. The sacrococcygeal joint is a hinge joint that joins the sacrum and the coccyx.  

Muscles  

The pelvic floor consists of muscles that form the base of the pelvis. These muscles provide support to our internal organs. The pelvic floor consists of levator ani and coccygeus which come in pairs. Levator ani consists of puborectalis, pubococcygeus and iliococcygeus. 

The muscles of the pelvic wall are the muscles that line the pelvic cavity. This includes the obturator internus and the piriformis which externally rotates and strengthens the hip.  

The perineum sits below the pelvic floor muscles and contains muscles of the genitalia and the anus. 

Ligaments  

A ligament is a fibrous connective tissue that attaches bone to bone. The pelvis is held together by three main ligaments, the iliolumbar ligament, the sacrospinous ligament and the sacrotuberous ligament. These are the main ligaments that provide structural support to the pelvis. 

Blood vessels  

The main blood supply to the pelvis is provided by the common iliac artery which branches into the internal and external iliac arteries.  

The internal and external iliac veins come together to form the common iliac which transports deoxygenated blood into the inferior vena cava.  

Nerves  

The sacral plexus supplies the muscles of the pelvis which consists of the sciatic nerve, pudendal nerve and gluteal nerves.  

The coccygeal plexus supplies the coccygeus muscles and the levator ani muscles.