The sacrum is made of five fused bones—S1 is at the top ... The L5-S1 is also called the lumbosacral joint. It is the part of the spine where the lumbar spine ends and the sacral spine begins.

Medically reviewed by Jennifer Steinhoff, MDThe lumbar spine includes the five vertebrae in your lower back numbered L1 to L5 ...

There are 5 lumbar vertebrae in the lumbar region. There are 5 sacral vertebrae, which are fused as one bone and known as the sacrum, in the sacral region. There are 3 to 5 coccygeal vertebrae, which ...