What Causes Pain In Bone Island On Hip?

I was diagnosed (by a bone scan) with a bone island in my hip about two years ago. Last year (8/2010) I had a CT scan which showed that it was still the same size, however, in the past few weeks it has begun to really hurt. Is this normal? Sitting and laying down are the worst. It seems better with standing and walking, stretching seems to help, and I seem to notice it more with the summer humidity.