People have heard of the SI joint, though most don't know what it is.
The term stands for sacroiliac joint, formed when the sacrum (the fused part of the spin just above the tailbone) and the ilium (the large broad bone of the upper section of the pelvis) come together.
The SI joint is meant to stay closed with the sacrum and the ilium in a parallel position to one another.
However, nature has made this joint slightly moveable, versus fused, in order to decrease the chance of stress damage, much the way divisions in a sidewalk allow the slight expansions, contractions, and movements to occur without cracking.
During yoga asana practice and everyday movement, when the pelvis moves into a forward or backward tilt position, the SI joint, if not moved consciously, shears apart slightly at the top or bottom.
This shearing apart of the SI joint causes discomfort - the sensation of either over-stretching or compressing within the joint.
It is important to note excessive and repetitive shearing within the SI joint during forward tilting can lead to permanent joint laxity and chronic discomfort in the joint.
To control and maintain closure in the SI joint during pelvic movement, one needs to understand how the movement of the pelvis affects the movement of the sit bones and the thigh bones.
When the pelvis tilts forward, as in a forward bend pose, without conscious movement of the SI joint the ilium widens, causing the sit bones to narrow toward each other and the thigh bones to be drawn into the hip sockets.
This widening of the ilium causes overstretching in the SI joint and joint laxity.
To neutralize the SI joint, the thigh bones need to be abducted from the hip sockets.
This will cause the sit bones to widen back to normal distance, and the SI joint to close back to a parallel, yet closed position.
When the pelvis tilts back however, as in a backward bend pose, the ilium narrows, causing the sit bones to widen and the thigh bones to abduct.
This narrowing of the illium causes jamming in the SI joint, which in turn tends to create jamming in the lower back area.
To neutralize the SI joint here, the thigh bones need to be adducted into the hip sockets.
This will cause the sit bones to narrow back to a normal distance, and the SI joint to open back to a parallel, yet closed position.
Closure in the SI joint during yoga asana practice is important.
Not only to the health of this joint, but also to ensure both the maximum flexibility and stability within a pose.
If the SI joint is compromised, so too will be the proper yoga posture.
So remember these two simple rules for maintaining SI joint closure as you move through your yoga practice.