Walking on front paw wrists?

My guy, who is somewhere b/w 13 and 16, has been having some hind leg weakness and muscle decrease. Over a few years dropped about 3lbs. Went to the vet a few days ago, blood and urine completely normal. However, yesterday, I noticed him walking more on his front wrists. Maybe I just didn't see it before, but could this be arthritis? I'ma  bit confused.