I find that putting a small platform, say, 3-4" thick, the size of a briefcase or larger, helps a lot.
You should *never* have your legs dangling: that puts negative pressure on the knee and draws liquid inside the joint.
Suggestion: start a garden in your backyard and go hoe-out the weeds for ten minutes every two hours. You'll also get a better sun tan than by staying in front of the monitor.
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