If you have minor arthritis in your knees, what type of exercise makes them more flexible and less sore?

Stretching keeps you flexible and improves your range of motion, or how far you can move your joints in certain directions. It also helps you lower your odds of pain and injuries. Always warm up with a 5-minute walk first.

In my experience with arthritis, mostly my back, I get the most relief by staying in motion. I’m in the most pain when I wake up, and it starts going away once I’m up and around 

What arthritic knees require is the strengthening of the supporting structures--that's the muscles, tendons, and ligaments. Any exercise that works the knee without causing pain moves you toward that goal.

Walking is excellent, although you may need to go slower than you once did, or you may require a surface that's pretty much level rather than irregular like a hiking trail. For a fitness challenge that won't hurt your knees, climb shallow steps.

Cycling is great if the flex required isn't so deep it hurts. Regular bike or stationary are both fine. The same is true of rowing machines or actually getting out in a boat.

Yoga and tai chi are also good, and something you may be able to continue even as your knees get worse with passing years. Both also help with strength and balance, important as you get older. (Raises hand.)

Swimming is probably the least joint-damaging exercise there is, but it probably won't help your knees improve. Still, it's a pleasure when the water's just right.

i would ask your doctor about it

Any exercise that does not put a lot of pressure on the knees, such as; swimming/cycling/aerobics.

In general, yoga. Walking is also good. When I was fencing, I also used deep knee bends with my feet flat on the floor.