Most injuries, and balance problems, happen in the areas between the major weight segments of the spine — atlanto-occipital, cervico-thoracic, lumbosacral. An additional joint that’s sometimes overlooked is the sacroiliac joint, situated between the low back and the hips, on the back of the pelvis. When you have low back pain there, it’s often the S/I that’s troubled. And if you have hip problems, the S/I is almost definitely involved, as it’s an accessory joint to the hip. The pain can be sharp and pointed, and can even refer down the back of the leg, mimicking sciatica.
Go find a skeleton and look at it from the front (if you don’t have a skeleton handy, look at a picture or just imagine it). The bottom of the spine is the arrowhead-shaped sacrum or tailbone. Before you evolved into a human, it was the beginning of your tail (remember?). The ilia are the two bones that look like Mouseketeer ears on either side of the pelvis. The S/I joint is located between the tail and those two bones. It assists the actions of lifting your leg to either the front or the back, and it’s very important to graceful gait, because it switches from a locked position (so you can stand up on one leg) and an unlocked position (so you can swing your leg forward in space to walk).
Traditional anatomy ascribed no movement whatsoever to the sacroiliac joint and considered the pelvis to be one solid amalgam of bone with legs running around underneath and the spine moving around on top. The anatomists thought this way because they figured everything out by cutting up a dead body. But the living body – and certainly, the S/I joint – moves quite differently than a dead one.
Movement-centered touch professionals argued – and it is now accepted – that the sacroiliac joint is moveable and plays a significant role in assisting the action called “hip flexion” (lifting the leg to the front) and a smaller role in “hip extension” (lifting the leg to the back).
The remarkable acts of standing and walking are endlessly dynamic and never fixed. Stability is dynamic, meaning that we are always moving, falling, and catching ourselves in small and large ways. Too much stability is rigidity; too much mobility is collapse. Finding the balance between mobility and stability is the goal of movement practice and core strength.
One of my most influential mentors is Irene Dowd. To teach me what dynamic stability is, she told me to start thinking as if there were no pelvis. Instead, I imagined my spine ending in my tail and legs that started at my Mouseketeer ears. In between? The S/I joint.
If you think this way, balancing – on two legs or one – becomes a continuous dance with gravity and the sacroiliac joint is constantly moving and adapting to movement to keep us moving freely with balance.
It’s much easier to feel and understand the concept of core strength if there’s no fixity to the segments but rather a delicious play of muscles, joints, and the nervous system, continuously generating new ‘equilibriums’.
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