I am an aerobics enthusiast. I do aerobics in the square every night. Never heard of wearing knee pads. You hardly need to wear knee pads to do aerobic exercise.
Aerobics is almost marching aerobics, mainly in the upper body, arms, legs and feet.
If you have ever hurt your knee, just wear a kneepad, which is very comfortable. I think any brand and kind of knee pads can be chosen at will.