Sciatica is specifically nerve pain involving the posterior aspect of the thigh, calf or foot and which is caused by irritation or compression of  the sciatic nerve, the main nerve into the leg.  Pain may originate where the nerves pass through and emerge between the lower bones of the spine (lumbar vertebrae) or as the nerve passes through the Piriformis muscles in the pelvis.. There may be numbness and weakness of the lower leg muscles and loss of reflexes.

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