The lumbosacral plexus is the anatomy of the low back and pelvis that forms the major nerves of the lower abdomen, pelvis and lower limb. It is not as susceptible to injury as the brachial plexus so clinically we understand the anatomy of this plexus a little differently, but it is important to be able to recall the spinal nerve roots of the major nerves here and the functions that will be lost if injured.