i have just the solution for *you! stand up leaning every so slightly forward, so the majority of your weight in on the balls of your feet. tense your quads, which should force your knees backwards. once balanced, repeat in short sharp pulses.
once used to the feeling it's probably easier to do whilst sat up in bed on across a sofa.
(*it worked for me, no idea if it will help you)
Diagram please. I just tried and it felt like I dry humped the room.
Diagram please. I just tried and it felt like I dry humped the room.