When the sacrum tilts due to an Ilio-sacral subluxation, the coccyx also tilts. As a result the structures between the lower edge of the sacrum and the upper edge of the pubic bone react like a joint. The sacrum makes, when it tilts, a movement towards the back. The upper edge of the coccyx also does this movement. The tip of the coccyx however remains, being hold by tendons and ligaments, in its original position. Thereby the angle between the inner side of the sacrum and the inner side of the coccyx becomes smaller.
This process I have called tilt of the sacrum.
The classical medicine calls this finding a fracture of the coccyx.