I saw Machu Picchu when I saw it 40 years ago!!! They had an old train that just crawled up the mountains. When I was there, it was just mostly ruins with no nice little signs telling you what everything was----but it was magnificent.
However, I do remember how hard it was to walk---I would take 12 steps and then huff and puff for a while---I was five months pregnant when there too!! I agree with Pumpkin that you will need a second opinion at some point---many docs in S. America were trained in the US and they speak English. But, for now, it appears that you had your tkr in Feb, 2014 and then had a MUA in March of this year. That is a lot for your poor knee to take.
Now 6 months later, you are still stiff and sore. How long have you been traveling around SA? Here are some things I would try if I were you: 1. I would get a cane or two hiking poles to help with your gait so that you do not limp. 2. I would elevate the leg--toes above nose as much as I could. Put your leg on a chair while you eat lunch, even. 3. I would wear support hose of some kind, if you can find them, to keep the swelling down as much as possible. 4. I would take every opportunity to rest----shorter hikes, shorter shopping days.
Are you wearing pre surgery hiking boots? If so, they have the wear patterns of your old knee---mine hurt my feet and made my gait less fluid. it was a relief to get all new shoes. For now, you will have to accept that your knee is not 100% and give yourself more rest breaks.