What causes sacroilliac joint pain?

The SI joint or sacro-iliac joint is located in the pelvis where the sacrum and ilia meet. Many people suffering from pain in the back of the pelvis are told they have SI joint dysfunction. But what does this mean? The tensor fascia lata (TFL), rectus femoris, and sartorius muscles cause problems at this joint. They can become tight and rotate one side of the pelvis forward, which can cause shear at the SI joint. This happens because these three muscles are attached onto the ilium, not the sacrum. The ilium rotates forward a little more than the sacrum, which twists the SI joint. A relatively pronated foot may also be contributing to these issues, although this is rare.