I just got a new 1yr old lab mix from the pound. He was recently fixed and is sort of leaning to one sid when he sits. My friend's dog does the same thing, but she has bad hips. I was just concerned and wanted to make sure he didn't have bad hips too; or if it's just because he's sore after the surgery.

I'm almost 100% sure this is from the surgery. If you were just cut up down there, you wouldn't want to sit on it either. :P

Even still, sitting sideways like this doesnt always mean something is wrong. It could just be a comfortable change of position, unless he does it 100% of the time.