1knee 
/ˈni:/ noun
plural knees /ˈni:/ noun [count] 1 : the joint that bends at the middle of your leg
▪ I fell down and hurt my knee. ▪ She suffered a serious knee injury. ▪ His knees trembled/shook with fear. ▪ She dropped/fell/sank to her knees [=she knelt down] and begged for forgiveness. = She got down on her knees and begged for forgiveness. ▪ He got/went down on one knee and proposed to her. ▪ If you want to clean the floor properly, you have to get down on your (hands and) knees [=you have to kneel down on the floor] and start scrubbing. — see picture at human 2 : the upper part of your leg when you are sitting
▪ His little granddaughter sat on his knee. 3 : the part that covers the knee on a pair of pants
▪ Her jeans had holes at the knees. 4 : a forceful hit with a bent knee
▪ She gave him a knee to the stomach. [=she kneed him in the stomach]
▪ I fell down and hurt my knee. ▪ She suffered a serious knee injury. ▪ His knees trembled/shook with fear. ▪ She dropped/fell/sank to her knees [=she knelt down] and begged for forgiveness. = She got down on her knees and begged for forgiveness. ▪ He got/went down on one knee and proposed to her. ▪ If you want to clean the floor properly, you have to get down on your (hands and) knees [=you have to kneel down on the floor] and start scrubbing. — see picture at human
▪ His little granddaughter sat on his knee.
▪ Her jeans had holes at the knees.
▪ She gave him a knee to the stomach. [=she kneed him in the stomach]
bring (someone) to his/her knees
: to completely defeat or overwhelm (someone)
▪ The general vowed he would bring the enemy to their knees. — often used figuratively ▪ The increase in oil prices could bring the economy to its knees. [=it could greatly hurt the economy]
▪ The general vowed he would bring the enemy to their knees. — often used figuratively ▪ The increase in oil prices could bring the economy to its knees. [=it could greatly hurt the economy]
learn (something) at your mother's knee
: to learn (something) when you are very young
▪ I learned to speak French at my mother's knee.
▪ I learned to speak French at my mother's knee.
on bended knee/knees — see 1bend
weak at/in the knees — see weak
— see also bee's knees
