What to expect about TKR replacement with metal rod ?c

Had TKR in 2019 could not straighten leg enough to walk from day one and after PT. Seeing another orthopedic surgeon, we seem to think replacing old TKR with metal rod. Has anyone had this surgery done, if so what can I expect out of this pain wise and PT besides just a straight leg and a limp ? I am a 76 old wheelchair bound male .