The lumbosacral plexus. A grouping of nerves which stem from the lumbar and sacral portion of the spinal cord, the lumbosacral plexus provides the predominance of the nerve innervation for the lower limb.
Psoas muscle attaches to your lower spine and to your thigh bone. If it's tight (sitting too much?) it pulls your lower back. It's one of the common causes of lower BACK PAIN! If you can stretch this regularly then your lower back may feel a lot better!
The number one cause of lower-back pain is a tight hip flexor (or psoas). It happens to everyone and is usually caused by sitting down; another cause is sleeping on your side in a fetal position. (Lower Back Pain Sleep)
Important Muscles Involved in Lower Back Pain – Part 1 : Quadratus Lumborum
Quadratus Lumborum trigger point diagram, pain patterns and related medical symptoms. The myofascial pain pattern has pain locations that are displayed in red and associated trigger points shown as Xs.