both knees
Refers to both knees together, often used in contexts like kneeling, sitting, or describing a posture involving both knees.
He apologized on both knees.
Sit hugging both knees.
Compound of 諸 (もろ, 'both') and 膝 (ひざ, 'knee'). The prefix 諸 is used in a few words to mean 'both' or 'together'.