The Sciatica nerve runs from lower back (buttocks) down leg & can cause severe pain. I have had it for years & have had numerous and varied treatments for it. None worked, sorry to say. I have pain every day, and the only remedy/relief I have found is to sit down till it subsides.. Perhaps the nerve is being impinged upon somehow. The internet, (on reputable sites) is always a good source to learn about this problem.
I have not found a doctor that is able to help alleviate my pain even though they have tried everything from physical therapy to surgical procedures.