The sacrum and the coccyx each consist of multiple bones that fuse over time. L5-S1 consists of the last bone in the lumbar spine (low back), called L5, and the triangle-shaped bone under it ...

"This bone, which we call the L4 bone, is shifted forward on the L5 bone. That shifting can result in pinching nerves." Jan's MRI images show how much her nerves were pinched. The spinal column ...