expression
intimately; sitting knee to knee
Describes a close, face-to-face conversation or interaction, often with a sense of openness and sincerity. Literally 'with knees touching', it evokes a private, comfortable setting.
友人と膝を交えて話し合った。
I had an intimate talk with a friend, sitting close together.
膝を交えて語り合う時間は大切だ。
Time spent talking intimately, knee to knee, is precious.
Similar meaning of sitting face-to-face for a serious discussion, but 膝を交えて emphasizes the intimacy and closeness of the interaction.
From 膝 (knee) + を + 交えて (te-form of 交える 'to mix, to cross'), literally 'crossing knees', describing the posture of sitting very close together.