There can be a variety of root causes of sciatica, such as a herniated disc, degenerative disc disease, facet joint dysfunction, osteoarthritis and more. The center of a lumbar disc is filled with a jelly-like substance that can break through the outer layer and press on a nearby nerve root. This nerve compression can cause nerve root pain in the back. Keep in mind that the disc walls are abundant with nerve fibers. Any tear through the wall can cause severe pain. As people age, the lumbar discs lose hydration and wear down. There is no cushion for any impact. Tears can also develop and cause pain. This condition is known as degenerative disc disease.
Facet joint dysfunction can also cause back pain and sciatica. If the cartilage of these joints is damaged or not functioning properly, the end result can be back pain or sciatica. Osteoarthritis is associated with aging. It is a condition that gradually progresses. The discs and facet joints are worn down. It causes back pain, swelling and instability. Any trauma or compression fracture can result in sciatica, such as a car accident or a fall.