I’ve had sore joints due to pre menopause & I hurt my knee a couple of years ago so have been building up strengthening exercises recently. I don’t really walk anywhere though as it’s not particularly comfortable as my knees get stiff. However through regular cycling ( I was swimming pre lockdown) and daily HIT routines I’m feeling more confident to go out for a walk. But I’ve just come back from 15 minutes 1500 steps & an exhausted and my knees are stiff. What’s the best way to built up stamina so I can comfortably walk for an hour or more?