A long title! I had a right knee replacement two years ago and did fine. The left knee needs replaced as well, but covid hit and I put it off. Over the past few months my right leg (the leg with the new knee) started giving out and then I had upper thigh pain, which got worse until now it's difficult to walk or climb stairs. The pain is front right thigh and sometimes back of the thigh or front left. If I sit on the floor with my knees bent and feet together, I can push my left knee down to the floor but can only get the right down halfway. My GP thought it might be bursitis. I was afraid I might need a knee revision, but went to the surgeon for x rays. The knee replacement is fine but my right hip has severe bone-on-bone arthritis and spurs. Do I assume my recent pain and lack of flexibility is the bad hip or could it be a back problem? How do I know? My left knee is also a disaster, but do I replace the joint that's giving me the most pain and lack of mobility first? Eventually, the surgeon said, I'd have all four joints replaced. Lucky me. This has taken me completely by surprise, though it shouldn't have. I just turned 70 and have had arthritis for decades.