good day fellas, I'll pass my experience on, blew my ACL out in 89, ortho doc then said I could be a guinea pig, and do an ACL replacement and do 6mo of PT, but without insurance and newly married in college, it wasn't an attractive offering, also he did offer I could start cycling and build up my accessory muscles and...probably be as well off for some time. As a Nurse Practitioner, that was a good choice for me, and now 30+ years later, at 52, I had a total knee replacement. Raced prior up to cat 3, love cycling, but the 2-3 years prior to my replacement my knee felt unstable and like a cheese grader during rides and I was literally limited in that, my knee would effuse/swell after 1hr rides, and even working in my office it was limiting me. My MRI of the knee evidenced that, and it was bone on bone and no injections helped. My ortho doc was hesitant to offer replacement but I insisted, and said now and not at 75 when I won't be as active, and if you don't, I'll find one who will. He was sport med fellowship trained also and agreed. I was asking about activity quite a bit in relationship to knee replacement longevity and initially he couldn't really answer that. Anyway, I was back in 3 wk to work, painfree, and on the bike. But, on the bike, the first year I admit I was hesitant as I don't want a 'redo' knee surgery since he didn't really have any info on that. He couldn't provide any literature on long term knee data in cyclist, so I backed my riding down on my own intuitively, but just last month he sent me a recent study that did evidence long term observational data that cycling specifically did not change outcomes or need redo surgery due to cycling itself, so it made me more comfortable riding longer and more frequently now. After you have surgery, you will notice your artificial knee will make noises, and when I ride mine squeaks quite rhythmically so that was why I was hesitant. It clicks, but no problem. On the bike, it feels great from a power standpoint as my prior knee was with laxity and I could literally feel that. I think another key is that you don't want any needless accidents or injury after a surgery like this. Nonetheless, hope my experience helps others.