What Causes Sciatica Pain And Clicking Sensation While Straightening Leg?

I am a USPS letter carrier. As you can tell by my job, it can be very strenuous. I have sciatica down my left leg and doctor did surgery for a L5S1 fussion. I was off work for 8 months. I am sad to say that the sciatica is back and even worse. When I am moving I am okay, but when I stop moving that is when it acts up. My dr. said it is not my back, b/c it is stable and not showing signs of a 2nd herniated disc. Could I have a labral tear in my hip? I am at a loss to say how frustrating the sciatica is. Another symptom I have is a clunking noise that happens while doing PT when I straighten leg to its fullest.