I sympathize with your struggle as it sounds like a catch22. I didn’t have knock knee but arthritis in knees, hip and shoulder. Had right knee replaced in 2018 after years of suffering, PT and every kind of shot or injection they recommended until they thought I was old enough so I would not have to do a second time. It took several years before it felt “normal” so I decided I would not do the left knee until it felt worse than the right. Well, in March 2022 my left hip decided it wanted in on the party and went down hill so quickly I had to use a walker. I had it replaced immediately and it was a miracle. I was walking with a cane and within 2 weeks nothing. Then my right shoulder insisted it get the attention I have been ignoring for ten years and it was replaced five months later. The next year my left knee started to get worse and since my other replacements brought me such pain relieve I did it before I “had”to. My point is, you never know what is going to happen or when. If I would change anything it would to have gotten the replacements sooner rather than later. (btw, I just turned 70 and during all the above my husband went on hospice, (another miracle) ; covid hit, postponing my son’s wedding in Jamaica, that I had to miss anyway) You just never know. Whatever decision you make will be the right one!