Spondylitis can also feel this way. I suffer from Ankylosing spondolytis it and it waxes and wanes. It starts as lower back pain and then moves into my left hip and gluteal area. It tends to hurt severely when I have been moving about and then I move into a reclining position... I believe cyclelops has the right idea, a cortisone shot, or even a dose pack of prednisone. Usually works for me.

Hope you feel better...

Mere