Sciatica most commonly occurs when a herniated disk, bone spur on the spine or narrowing of the spine (spinal stenosis) compresses part of the nerve. This causes inflammation, pain and often some numbness in the affected leg. Although the pain associated with sciatica can be severe, most cases resolve with non-operative treatments in a few weeks.

Herniation occurs when inner disc material begins to push out through a tear or weak point in the outer layer. If part of the disc constricts or irritates part of the sciatic nerve root in the lower spine, the symptoms commonly referred to as sciatica can develop.