Just a thought here but have you checked the bottom of the feet? S/he may not be walking a lot because s/he has injuries there. Everyone keeps asking about the legs but I never saw anyone mention the bottom of the feet. If they are dirty, wipe them off with a damp rag. If you see anything, snap a pic and post it. After running around on city streets, s/he may have some injuries down there that just plum hurt to walk on.