I do a combination of "power walking," day hiking, stationary bike (primarily to strengthen lower body muscles without impacting joints) and a weight program involving many reps with relatively light weights (also to strengthen muscles without injuring joints). I also bought a cheap 2x4 which I walk several times daily to improve my balance. It helps!

For me, day hiking twice weekly is the best. Far less stress on the joints than power walking the local sidewalks (which I may have to give up), more uneven ground, more hills. It's also a lot more fun for both me and my dog! Of course, I realize that not everyone has Columbia River Gorge trails 20 minutes' drive from their house! Nor is everyone retired and able to get out on weekdays! You have to make do with what you have in the time you have. The important thing is to get out and move several times weekly!