Lumbar Spine Anatomy and Pain    The lumbar spine has several
distinguishing characteristics:    • The lower the vertebra is
in the spinal column, the more weight it must bear. The five
vertebrae of the lumbar spine (L1-L5) are the biggest unfused
vertebrae in the spinal column, enabling them to support the
weight of the entire torso.   • The lumbar spine meets the
sacrum at the lumbosacral joint (L5-S1). This joint allows for
considerable rotation, so that the pelvis and hips may swing
when walking and running.   • Article continues below   • The
spinal cord travels from the base of the skull through the
spinal column and ends at about T12-L1 - where the thoracic
spine meets the lumbar spine. At that point numerous nerve roots
from the spinal cord continue down and branch out, forming the
"cauda equina," named for its resemblance to a horse's tail.
These nerves extend to the lower extremities (buttocks, legs and
feet). Because the spinal cord does not run through the lumbar
spine, it is quite rare that a low