A compressed nerve results when the nerve roots in the spinal cord are irritated or pinched. Sciatica is the lay term usually used to describe the pain caused by compression of the spinal nerves, and radiculopathy and radicular pain are the terms usually used by clinicians.
In the low back, the nerves most often compressed are at L4-L5 and L5-S1, at the very bottom of the low back. If a nerve is compressed in the low back, the affect of the disc material against the nerve root causes pain to radiate into the buttocks and back of the thigh and calf, and may extend down to the foot.
Numbness, tingling, and/or a burning or prickling sensation are also common symptoms. If a nerve is compressed in the neck, the symptoms may radiate down the arm.