Slipped disc. Posterior, three dimensional, coloured computed tomography (CT) scan of the pelvis of a patient with a slipped (ruptured) lumber disc. The intervertebral disc above the fourth lumber vertebra (blue block, upper centre) has ruptured and is protruding into the spinal canal (gap, centre). This puts pressure on the nerves running along the canal and results in pain, which is often felt down the legs (sciatica). Treatment is with physiotherapy and drugs, although surgery may be needed in extreme cases.