My wife had a partial knee replacement 5 years ago and it has been a boon for her and since the op she has done two TGO challenge events (coast - coast across Scotland), plus the WHW and loads of other shorter outings on the Hills and Fells so much so she has now worn the other knee out and is having that replaced in August.

This of course is just my wife's experience and I guess it is not the same for all that have it done, but good luck if you have the replacement.