I hate to be negative, but sciatic nerve pain can also be caused by something pressing on the nerve. X-Rays will often come up clean and not show some problems. Ten years ago, when I had my first hip done, orthopedic surgeons would do MRIs at the drop of a hat - I had many. But in the past five or six years, insurance companies started refusing to pay for MRIs in some cases, so doctors use them less now. They have to be able to prove to the insurance company the necessity. (This is why my second hip replacement was such a miserable experience.) I hope it is just inflammation. Sciatic pain is something most people cannot begin to understand. I liken it to having an invisible stalker hitting you randomly with an electric cattle prod.