The lumbosacral joint, also called L5-S1, is a term used to describe a part of the spine. L5-S1 is the exact spot where the lumbar spine ends and the sacral spine begins. The lumbosacral joint ...

It contains the following: Sacrum. A spade-shaped bone that is formed by the fusion of 5 originally separate sacral vertebrae. Coccyx (tailbone). Formed by the fusion of 4 originally separated ...