Spinal Mechanics

Physiology of the Spine

The simplified illustration on the left, shows the facets of an ilium with the associated a leg positioning during a typical walking stride.

To begin a forward walking movement the anterior iliac facet engages on the side of the leading leg. This action levers the leg into a superior, antero-medial direction. Shown in magenta.

The person then leans their weight into the leading leg. This action engages the guider anterior facet below and angles the leg into the starter position for weight bearing to follow.

When the foot touches the ground,  resistance returning up the leg levers the ilium to engage the guider posterior facets of the sacrum. At this point there is a momentary equilibrium of body weight distributed on both legs. Shown in blue.

As body weight continues to bear down on the leg, the ground resistance that  is  returned  up the leg  lifts the pelvis on that side. This causes the person to move further forward.

Bayliss  Sacroiliac Theory

The illustrations below show part of the theoretical sacroiliac facet action taken during the walking action. Humans have  two legs and so a reciprocal action needs to take place on the opposite side for the person to move forward. To find out how this action takes place and learn how the spinal column takes advantage of the sacroiliac facet contours to rotate and side-bend in forward and backward bending, you will need to purchase the DVD.

The  beauty of  the ‘Bayliss Sacroiliac Theory’ is that the sacral facets stay within the confines of iliac facets and comply with the line of  the ligament fibres.  

                                            Animation of Facets

The animation shown is not the complete sacroiliac action. The full action is explained in more detail within the DVD which can be obtained from spinalmechanics.com

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