As one well in my 82nd year, I do have some joint and foot pains but not serious enough to be unable to walk steps with groceries in and out of subways, buses, and walk up to a mile, even tho my first problem in right foot sole and left knee first appeared some 20 yrs ago. I read up all Arthritis magazines and found movement -- stretch and strengthen -- is the way to deal with it -- as probably it does good to so many other health issues, including mental health.

While occasionally I get some tightness feel in a leg, it disappears after stretching in All 3 Possible Directions in space: Sitting or standing. Foot: In and out, up and down, inwards and outwards. The idea is to feel the stretch in the leg, usually midcalf.
Similarly for upper legs, I move each of the legs while standing on the other, supporting if u need, with hands on a chair or wall.

I also believe we can only have optimal fitness which would be different for each person, EVEN in different Ages or Condition of one's body. Our bodies are our allies and will tell us when it's too little exertion or too much.
Good luck, fellow human!

Have the dr check your magnesium levels.
Also read about DMSO for arthritis.
It was an old drug taken off the market, but coming back for all sorts of ailments.

Try walking in the swimming pool at the 4 to 5 foot deep area.