The location of lumbar 5 sacral 1 is about below the waist, the first place to confirm this place is to confirm the lumbar 4 vertebrae, before confirming the lumbar 4 vertebrae should first confirm the location of the iliac crest, the iliac crest is the place where the hands point when the waist is usually forked, this place is exactly flat lumbar 4 vertebrae spinous process, lumbar 4 vertebrae down one is lumbar 5 vertebrae, and then down one is sacral 1 vertebrae. Lumbar 5 sacral 1 usually causes protrusion of the lumbar disc, mostly after prolonged sitting, squatting or bending and lifting heavy objects, resulting in rupture of the annulus fibrosus and extrusion of the nucleus pulposus. When a lumbar disc CT is done, there is often a protruding disc in the lumbar 5 sacral 1 area, and the location of the protrusion described above can be well confirmed in this way.