on bended knee
From Longman Dictionary of Contemporary Englishon bended kneeon bended kneea) ASK FOR something/ASK somebody TO DO somethingtrying very hard to persuade someone to do something He begged on bended knee for another chance. b) BENDin a kneeling position He went down on bended knee and asked her to marry him. → bendExamples from the Corpuson bended knee• George asked her to marry him on bended knee.• The TV network begged her on bended knee to return to the program.