In the first picture, I see the normal "lump" of the hip bone on the right side. In the second picture, there appears to be a hump that isn't the hip bone - just toward the front of the animal relative to the left rear leg. Also, you mentioned above that the lower half of his body is often bent in a certain way. Both these symptoms seem similar to the problem I had with mine, although I hope I'm wrong.
Keep us posted.