Your left knee.
Supposedly, it is traditionally done with the the left knee on the ground and the right knee up. All in all, though, there are are probably more important things to worry about when proposing and I think that your significant other probably won't mind with the whole importance and excitement of the event.
Turbo hustle
cuppid shuffle i think
When asking someone to marry you it does not matter if the male kneels on his left or right knee. Generally it is the right knee.
right knee left knee kidney wienie
Turbo hustle
left brain
She will propose a new plan to the board at the meeting.
get on your knee.
when your leg is removed right below your knee cap
On one knee.