Can you back pass to the goalkeeper off your knee?

Answer 1

You can use any part of your body (except what is considered hands of course) to pass back to a Goal Keeper.

An IDFK is awarded if a Goalkeeper picks up the ball with their hands after a teammate has deliberately passed the ball to them with their FOOT. There is nothing specific to knee/hip/thigh...etc. As long as the act is deemed deliberate in the opinion of the Ref and there is no intervening touch on the ball or deflection than an IDFK s/b awarded at the point of the infraction.

"In the opinion of the Ref" is very key in all laws of the game. What one might see as obvious the Ref may see as a misplayed ball (or not deliberate) - more so at the youth level. A 10yr old may have his head down trying to defend a player towards his own goal and puts a touch on the ball and the Keeper sweeps the ball up. Is there a deliberate attempt?

This rule was put into the game to stop the "delay" tactics teams were using in the early 90's when the GK could be used as a "Shield" of sorts.