Back pain, particularly sciatica, can be caused by a variety of factors. Sciatica specifically refers to pain that radiates along the path of the sciatic nerve, which runs from the lower back through the hips and buttocks and down each leg. Common causes of sciatica include herniated discs, spinal stenosis, and degenerative disc disease. Other contributing factors can include muscle spasms, pregnancy, and conditions like piriformis syndrome.