Can't give you an answer as I haven't had it- but Long term you are not finished yet.

Couple of years ago and riding on the MUP and a rider caught up with me. I knew him as A rider on the Local metrics about 5 years before but he did have a Knee problem that eventually stopped him riding. 18 months previously he had one of the knees replaced and as soon as he recovered- he had the other one done. He had started riding again- only on the Mups and flat rides but wanted to know if the Gridiron ride was still being done. He finally felt that he could tackle a longer hillier ride and thought this would be a good one to start with. If he was thinking about this one- he must have recovered fully.