Sciatica is a symptom. Did you know that? It's just a term to describe the painful pain that starts in your bottom/ lower back and runs down the leg.
But if it is a symptom, then what is the cause?
Well in some people, the piriformis, a muscle which sits on top of the sciatic nerve can go into spasm which compresses the nerves giving those sciatic symptoms.
So that pain down your leg, tingling in your toes or calves may be caused by the piriformis being in spasm.
This is actually the most common cause that I have personally come across. There are other possible causes too which is why it's important to assess and not just guess.
But the cool thing is that once you know the cause, you'll know exactly what you need to do to!