Which would be better for a 70 year old: knee joint replacement or physical therapy?

Depends: If the knee is severly arthritic and deformed with constant pain no question the knee replacement is by far a better option.Pt does not correct the arthritis , it help to srengh the muscles around the knee, improve the rom and muscles contractures.One is not subtitute for the other, they complement each other.

Depends: If the 70 year-old is healthy and mobile then knee replacement. If 70 yo is debilitated then pt.