Hi James,
I am hoping that you feel better, and this info. is TOO LATE for you!
But--my experience clinically is that often hip pain and low back pain go hand-in-hand, and so I am hopeful that someone may find this of use.
I'm a P.T., and this year had both a (failed) arthoscopy on my hip and about 2 weeks ago a (hopefully wonderful) resurfacing. I have a history of low back pain (have had two low back surgeries). My experience following both the arthroscopy and the (anterior approach) resurfacing was of increased low back pain, new sacroiliac pain, and increased sciatica. It all makes sense to me given the mechanics: After both hip procedures, I initially had decreased hip extension (my leg doesn't go as far behind me--this means that the low back will arch to compensate while walking), as well as post-operative swelling in the iliopsoas muscle, which attaches at one end to the low back, and at the other end inside the pelvis. So, when this muscle is impacted, it pulls on your low back, increasing the ''arch'' in it. This muscle is also the major muscle for bending the hip (as in bringing your knee towards your chest). Following the reduction in swelling from the arthroscopy, I was able to diminish much of the low back and sacroiliac pain by doing self-release of the iliopsoas muscle--not fun! Basically you dig your thumbs inside the iliac crest (the front part of the hips that you can feel on either side of the belly button), holding pressure on the sore tissues until it ''softens'', and then you follow it a bit deeper with your thumb. A skilled masseuse or P.T. can do more effective iliopsoas release than you can do on yourself. The other component that was very helpful to me following the arthroscopy was a LOT of self massage of the I-T, or iliotibilal band (long tendon on the side of the leg that runs from a small muscle at the side of the thigh to the knee).