Spinal Mechanics

Copyright © John Bayliss - spinalmechanics.com  est 2005                                                                                                                                                   About us  -   Contact  -  Links

Structure Governs Function

Past research on the sacroiliac joints was based on structure governs function and focused on the internal workings of the sacroiliac articulations. The outcome of that research shrouded the joints with an unfathomable quality, rather than understanding.  Like the kings clothes, everyone could see the sacroiliac theories meant that the facets at some point would be placed in a state of semi-dislocation but nobody wanted to be the one to say. This is because the subject had been ‘researched’ with highly accurate equipment. There are two main semi-dislocation theories commonly acknowledged. ‘Nutation’ and ‘Three Pole


Common sense

Common sense went out of the window. When you stop to think, it is highly unlikely that who ever it was that designed the human body and mind would be stumped over the articulation of the sacroiliac joints. When you understand how  the sacroiliac joints articulate you realise it is a very clever but simple joint.


Function Governs Structure

Back in 2004  John Bayliss worked out how the sacroiliac joints articulate during walking, without semi-dislocation. To achieve this, he had to forget all that he had been taught and read and look at the joint without prejudice.  


Thanks to John Bayliss’s work, we can now categorically say that the iliac sacral facets are: A set of elongated contoured facets, divided by a mid rail of which the top facets are weight bearing and the lower facets are leg guiders.


The sacroiliac joints are cleverly designed and in keeping with other parts of the body they have more than one function.  These additional functions include the accommodation of pelvic side-shift, bi-lateral weight bearing and non-weight bearing whilst articulating. Liaison with the hip joints and the facets of L5. It also accommodates and guides spinal facet architecture and articulation. To understand how all these aspects fitted together John Bayliss had to think from the point of view of ‘function governs structure’. How the sacroiliac joints work is explained and illustrated in detail in his new book ‘Advanced osteopathic Manipulation’

Bony Ridge

Load bearing facets

Non load bearing facets

Iliac Facets

Structure Governs Function

Back to the top