Walking Backwards: Boost Balance, Strength, and Mind Power

For the past few years, I have had problems with arthritic knees, barely able to walk, etc. Along with other exercises, I was advised to walk backwards, preferable up a mild, not steep, incline to strengthen knees. There are youtube videos about this; I wasn't interested in the one where one pulls some device in a gym, but walking backwards on the driveway, or in the backyard, or safely in a park is worth it as it strengthens muscles you didn't know you had!