Lower back


Bones

Lumbar vertebrae (L1-L5)

Muscles

Erector spinae group (iliocostalis, longissimus, spinalis)

Multifidus 

Quadratus lumborum



Ligaments

Anterior longitudinal ligament

Posterior longitudinal ligament

Ligamentum flavum





Nerves

Lumbar spinal nerves (L1–L5)