I am a 58yr old male,I damaged my left knee playing inthe Police football team some 20 yrs ago. I had the cartlidge removed but over the last 5 yrs started to get arthritis in the knee. To be fair i get occasional pain but not excessive. the knee feels very unstable and clicks when moves. If I walk a lot playing golf or cycling then it is painful but arthretic 75 tablets help. I dont want the knee to get too bad before considering a replacemnt. I have restricted movement in it and its very swollen. At what point should I even consider having it done?