I'm only an infrequent and distinctly amateur plumber but have both those problems due to other health issues and treatment. Knee problems are an occupational hazard, so try to avoid kneeling on them (sit or lie on the floor or sit on low stool), and where there are no options use gel lined knee pads. When standing up from crouch do it one leg at a time so avoid force on knee until it's at 90 flex (I know that's tricky when you are wrapped around some tricky plumbing)
For the Achilles circulation in your lower legs may be key. I massage my calves and do some foot rotations (both dir) before getting out of bed otherwise I pull them after one or two paces. The most effective way to stretch after some warm up is a 2 inch firmish foam block under the front of the foot then with straight leg lean forwards holding handy piece of furniture for support. Wonder if something like cycling (no vicious hillclimbs) might help the circulation.
Silly question:Can you give your rough area so somebody can recommend a good local physio to get you the best diagnosis as a start point.
Cheers,
Roy (amateur)
