Sciatica is a pain that travels down from your lower back or buttock, to your foot.
It usually happens when the jelly within the discs that separate the bones of your spine (vertebrae) pushes or bursts out of the disc and irritates the sciatic nerve.
Swollen muscles, joints or ligaments can also irritate the nerve causing sciatica.
The sciatic nerve runs down through the back, into the buttock, down the back of the leg and round to the outside of the lower leg and foot.
When the nerve gets compressed or irritated, the brain interprets the pain as coming from the buttock or leg instead of the back, where the problem actually is.
The pain is often a severe shooting pain, sometimes accompanied with pins and needles or numbness.