Sacroiliac joint

A crucial joint that connects the sacrum at the base of the spine with the iliac bones of the pelvis.

The sacroiliac joint is a complex structure formed by the connection of the sacrum, the triangular bone at the base of the spine, and the ilium, the uppermost and largest part of the hip bone. This joint is classified as a synovial joint, meaning it is a highly movable joint allowing for a limited range of motion, primarily providing stability to the pelvis and transferring weight between the upper body and lower limbs.

Terminologia Anatomica

articulatio sacroiliaca

System

Skeletal system

Function

The sacroiliac joint serves multiple essential functions in the human body. Primarily, it plays a vital role in transmitting forces between the upper body and the legs, which is critical for standing, walking, running, and lifting activities. Its unique structure allows for slight movements that accommodate the pelvic and spinal positions during various physical activities. Additionally, the joint acts as a shock absorber, helping to dissipate impact forces during movements. This is particularly important during activities that involve weight-bearing, such as jumping or running, where the body experiences significant stresses. Furthermore, the sacroiliac joint is integral to maintaining pelvic stability, which is crucial for optimal locomotion and balance.

Location

The sacroiliac joint is located at the posterior aspect of the pelvis, where the sacrum meets each iliac bone. It is situated just below the lumbar spine and forms part of the posterior pelvic girdle. Specifically, this joint is positioned horizontally across the sacrum, which sits in the center, and connects laterally to the ilium on either side. The sacroiliac joints are positioned symmetrically on both sides of the body, thereby providing a robust support system for the pelvis. This specific location is critical as it serves as the foundation for the spinal column and supports the body's weight when standing or moving.

Did You Know?

Sacroiliac joints can move slightly, allowing for a small degree of mobility which helps adapt to various physical activities.
Pain in the sacroiliac joint can often be mistaken for lower back pain, but it originates from a different area.
The sacroiliac joint has a unique structure with irregular surfaces that lock together, providing stability without excessive movement.