Is it normal for your knee replacement to snap when you put your leg into a frog leg type position?

Knee snapping: Yes. At the extremes of the range of joint motion, sounds like "snapping" are more likely to occur in both normal and artificial joints. The frog-legged position puts your knees through a relatively extreme position.

Clunk: A clunk is common wit hmedial lateral stress avoid strange poistion if they dont have a little medlateralplay then the joints are tight and too stiff makes you appreciate the original.