Sciatica refers to one sided pain that radiates along the sciatic nerve which can affect the low back, buttock, hip and leg. Sciatica can occur as a result of a herniated disk, changes to the structure of the spine or activation of trigger points in the piriformis muscle. Any of these changes can cause compression of part of the sciatic nerve and lead to back, buttock and leg pain. The hallmark of sciatica is pain that radiates from the low back to the buttock and then down the back of the leg.