The Sacroiliac Joint

The sacroiliac joint, or SI joint, is another common culprit of low back pain. In fact, up to 30% of low back pain can be attributed to this joint. It’s formed where the sacrum (tailbone) and ilium (pelvis) come together on either side of the body. It’s an important joint because it transfers weight from the lower body to the upper body and vice versa. Why does this matter? Well, every time you walk or run your SI joints distribute the shock from the ground across the pelvis, which reduces strain on the spine.

These joints also help stabilize the body so it can maintain an upright posture while walking or running. Not only do they transfer weight and stabilize the body, but they also allow for a small degree of motion. If this weren’t the case, walking, running, and giving birth would not be possible. However, because the SI joints do allow for some motion, sometimes too much or not enough can develop and lead to SI joint dysfunction.

Certain conditions such as osteoarthritis, trauma, pregnancy, and the aging process can cause this excessive or lack of motion within the SI joints. When this occurs, the abnormal motion can cause low back pain and alterations in mobility and stability.