I have had 3 knee replacements. The first one was at age 50 and lasted 10 years before it wore out.
Last December, I had both knees replaced at the same time. The only time they give me a problem is when I unload a few hundred sacks of grain or hay and then they are only sore for a day or so.
I have never gone to therapy. One reason is that it would be a 200 mile round trip, another reason is that it is not necessary if you use the new knees.
I live on a 4000 acre ranch and have a lot to do. The only time the knees really hurt is when I bend them to far, they don't bend quite as far as OEM.
The metal in the knee does cause muscle problems when in very cold water and being on you hands and knees on hard surfaces is hard on the tendons.
As far as the camper goes, no problems.