We don't have synonyms for knees yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are knee, kneel and kneed.
"1605: I could as well be brought / To knee his throne and, squire-like, pension beg / To keep base life afoot. -- William Shakespeare, King Lear II.ii"
"1605: I could as well be brought / To knee his throne and, squire-like, pension beg / To keep base life afoot. -- William Shakespeare, King Lear II.ii"