While recuperating from a total knee replacement, I have found it advantageous to walk up and down small hills. It’s taken four and a half months to do this, however. The incline provides me with a good overall leg workout, along with circulatory benefits. The decline seems to mainly work on my quads and knee flexibility.
And, I find it great to walk backwards up the hill. This is great for my hamstrings.
Sturdy, nonslip soled shoes are essential for this exercise.