Sciatica connected to upper back also?

Yesterday eve. a bad pain grabbed me in my back on the L, and for a few das. I've had it behind my L. knee a few times. I tried to stretch different ways and it went away. I had sciatica yrs. ago in the R. leg but can the upper back affect the leg? It doesn't pain in between. And the pain is back just in a small area of my back. Thanks in advance.