Hi Margaret! Yes, this is because the disc herniation is severe and at the L4-5 spinal level. The spinal cord ends at approximately L1-2 spinal level. The associated lower spinal nerves travel distally and exit several levels below. A disc herniation at L4-5 may come in contact with any of the above listed nerves as they travel distally prior to exiting the spinal column.
Let me know if you have any other questions, and happy Thanksgiving!