I Have A Pain From My Butt Radiating Down To

I have a pain from my butt radiating down to my ankle. When I get up in the morning, I can barely stand. It takes 30 minutes or so before I can put weight on my left side. After about 3 hours, the pain subsides and I can function at about 90 percent. I at first thought that it was a pinched nerve...sciatica, but it now feels mostly in the left leg bone...I can sit and lie without pain. But have to keep moving or it seized up.