Several medical conditions can cause sciatica; however, an estimated 90 percent of cases are caused by herniated (slipped) disks. The spinal column consists of three parts:
Disks are made of cartilage, a strong and resilient material. The flexibility of the spine is facilitated by cartilage, which acts as a cushion between the vertebrae. Herniated disks occur when a disk is pushed out of place, exerting pressure on the sciatic nerve. Less common causes include infection, lumbar spinal stenosis and tumors within the spine.