slipped disk
a condition in which the gelatinous interior of an intervertebral disk is pushed through a weakened portion of its fibrous coating, pressing on adjacent nerve roots and associated structures. This causes pain in the back, leg, or arm, depending on the position of the disk and the nerve involved, and sometimes nerve damage (resulting in numbness, weakness, etc.). The sciatic nerve is most commonly affected. The medical name for this condition is prolapsed intervertebral disk.