The lumbar plexus is fashioned lateral towards the intervertebral foramina via the ventral rami of the main 4 lumbar spinal nerves (L1-L4), which all go through psoas key. The larger sized branches from the plexus exit the muscle to pass sharply downward to get to the abdominal wall as well https://www.sgvascularctr.com/swelling-leg-treatment-singapore/