I had this happen to me after lumbar surgery (laminectomies, foraminotomies, and discectomy). I was great for maybe 2 months and was even careful to follow all post-surgical instructions about bending, lifting, twisting, stretching, etc. Then all of a sudden one day I woke up at night, went to step out of bed, and almost fell because I had no feeling in one leg. Then the horrific pain started from my rear all the way down into my ankle. The sciatica pain felt as though someone sliced me open the whole way down and poured rubbing alcohol into the wound. The pain was 24/7 and unrelenting. I had new MRIs done and it was found that I had scar tissue, even though I did everything I was told to help prevent it. (I had to get two MRIS done - one with contrast and one without contrast because I had recently had surgery). Anyway, I went to get another ESI and that Doctor was actually able to flush out a piece of stuck scar tissue during my ESI, which resolved my sciatica pain. So, it is possible you could have scar tissue as well.