Yes, it must be Knees as men did used to make a proposal, propose marriage, to his beloved. Some men still do. My hubby proposed to me on his knees whilst was bedridden( having a particularly tough day with my neurological condition) which was very romantic as even though looked a whiter shade of pale he wanted to marry me! Good luck thumbscrew :-)
Found the definition fo precent, yet, wait here for confirmation as to whether that is the correct answer as not sure either way yet sure another poster will be.