I know 50+ guys who resumed bicycle racing post-TKR, so I'm psyched to get back on the bike. TKRs became real reliable over 20 years ago and they have only improved since then. The weak points were always the prosthesis loosening up over time (from jogging, lateral stress, etc., the glue breaks down) or the plastic bushing that serves as the cartilage wearing out. The latter is solved, the plastic in my TKR is impregnated with some vitamin E compound and the wear curve on that stuff looks like synthetic oil, it simply never wears out. So the final weak link is the medical adhesive they use to cement the joints in place, if they get that stronger you may see TKR replacements instead of ligament reconstructions and knee scopes in 10 years, because an artificial knee is in many ways injury proof (nothing to tear). Anyway, the TKRs are sort of promised to last 15+ years, but the ones from 20 years ago already often last 20+ years and the ones they do now are significantly better. There's a chance this bionic knee of mine may never require further intervention.