stand animation problem

Hi!

I have a script in a prim that uses the 'stand' animation to get an Avatar standing on the prim and then going down through a slope.

When the avatar starts to go down it bends the knees, it seems that it is floating. Why this happen?

I've also tried stand_1, stand_2, stand_3 and stand_4 it happens the same with all of them.

The animation 'land' works well (it doesn't bend the knees), but is not very appropriated for the effect that I want to get.

Do I have to make my own animation? If so, what do I have to do in order to get the avatar not to bend the knees when going down?

Thanks a lot.