Meditation Zabuton

Knees "squeek" after meditation... have you ever heard of this?
It's like the sound leather clothes would make.
Both knees are like this after about 30 min. of sitting seiza posture (kneeling with a bench) resting on a new zabuton (mat).
It does go away after 1 minute.
Why would this happen and is it very stupid to continue? And what can I do about it?
There is no pain.
I do martial arts where they incorporate meditation into our practice, and 30 mins in seiza is a good amount of time to have your knees in that position.
No it's not stupid to continue if there is no pain. And for most of us in our Kung Fu class, we have the same thing!



