The human posterior lumbar joint and spinous process are arranged in the shape of a stacked tile from the top down to the sacrococcyx, and the “distorted tile theory of sacroiliac subluxation” is a good way to distinguish the difference between sacroiliac subluxation and the pelvic rotation sign described abroad. The pelvis with sacroiliac joint subluxation is like a crooked tile, and no matter how it is placed, the pelvis cannot be balanced, so the photograph of frontal projection also shows that the upper edge of the iliac ridge on both sides is not equal. The lower lumbar vertebrae cannot be identified because of lateral deviation. In contrast, the simple type of pelvic rotation without sacroiliac subluxation is mainly caused by the lateral bending and lateral swing of the lumbar vertebrae, the structure of the pelvis is stable, the equilibrium state can be found, and the pelvic axis can be determined on the pelvic film and the superior border of the iliac spine on both sides is equal. Therefore, we believe that “the skewed tile theory of sacroiliac joint subluxation” and “five-line pelvic measurement method” are complementary, and are powerful theories and methods to prove and diagnose sacroiliac joint subluxation.