What Causes Brown Spots And Bruises On Hips And Upper Thighs?

I have had more than one health problem in the past-Hyper thyroid/graves disease which has caused osteo arthritis, and many other side effects. Also I was once told that there was a possibility that I had Hepatitis C. The doctor told me it could be showing up on my blood test due to the extremely high thyroid. I don't know if there is any connection to the new condition or not.The last few months I have noticed that I have brownish spots, looks like bruises on my hips and upper thighs. I keep getting a new one every month or so and they are not going away. Do you have any ideas what these could possibly be caused from?
Marcia Roberts