The sacroiliac (SI) joints are between the sacrum and each ilium of the pelvis. It plays a vital role in the biomechanics of the hip region.
Instability of the SI joints are sometimes causes of low back and hip pain. The truth is, your painful SI joint may have excess or abnormal motion rather than restriction, and it's possible you shouldn't try to stretch it out in an attempt to reduce that pain.
The SI joint is stabilized by the structure of the joint (ligaments and bony alignment) as well as dynamic muscular control from deep core muscles. Injury to the region, generally in the form of a fall directly onto the hip, can cause instability or hypermobility. As the joint moves with poor stabilization, there is increased stress on soft tissues. Often, this presents as buttock or tailbone pain that does not radiate into the thigh.
Often, patients will complain that the painful hip feels tight, and they attempt to stretch in various ways. The reason this is typically not the answer is because the joint is already moving too much, and increased range of motion generally aggravates soft tissues.
Restriction at the SI joints can be pain free locally, but may manifest itself as opposite side hip bursitis or SIJ irritation. Imagine that two wheels are rolling down a rutted dirt road with an axle between them. If one is stuck in the mud, it becomes a pivot point. The other wheel now deviates out of its rut and crosses the midline. The wheel that became stuck did not perform any abnormal motion, but rather demonstrated a lack of motion. The wheel that kept moving had to move across the midline in an area that it would not generally move through. Typically a restriction at an SI joint can be picked up as a restriction into standing trunk sidebending to the same side, decreased straight leg raise versus the opposite side, and decreased hip internal rotation versus the opposite side.
It would be nice to have a one-size-fits-all program to resolve SIJ pain and dysfunction, but the reality is that it's not that simple. Treatment typically involves altering biomechanics through mobilization or manipulation as well as a graded program of core strengthening to improve motor control.
The bottom line is that if you have pain at one of your SI joints, and have tried in vain to improve the situation with various hip stretching techniques, you may want to check with a good manual physical therapist who can determine if that SI joint is restricted or hypermobile, and whether it is able to stabilize during functional activities.
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