Animal Care Needed

Have an old yellow lab having trouble going for walks and especially young upstairs once hes done . Hes ok with 7 outside steps but cant and refuses going up the 6 inside steps to our apartment. Gets frustrated and aggravated when we try having him come up. He is a 10o pound lab , he wears a harness with front and rear handles , my wife and I cant manage him if he doesnt help , and he doesnt he has arthritis especially rear end please advise if you can help