Hi guys, i have a little stupid issue,maybe someone know how to solve it?

I have IK chain setup, but when i move knee of a character, other geometry change it's orientation.VIDEO [youtu.be]
I'll really appreciate any help

From the video it looks as if the IK chain is working properly. The change of orientation when you move the knees is a function of all IK chains. They need a pole vector to tell them in which direction to solve. That is why you would normally offset the knee control / twist control joints (normally forward) in the direction you want the IK joint to solve.

You can do some optional things to help maintain the orientation. A lot of times I'll offset the knee joint forward and then parent it to the ankle. That usually helps it stay forward of the ankle and keep a consistent orientation. But in complicated movements you often have to animate the knee to maintain the proper orientation.