The knee is a part of the leg. It’s between your thigh and your shin. It’s the joint that allows you to bend your leg. It has a knee cap which protects the joint.
A knee looks like this:
get on one’s knees
A person gets on his knees when he goes to the ground.
A doctor checks your knees when you go in for an examination.
Knee pads help protect your knees.
She’s wearing knee pads.
When a man proposes marriage, sometimes he gets down on one knee. (This is a custom.)
He got down on his knees to get some water from the river.
Some people get down on their knees when they pray to God.
A person who is "weak-kneed" is nervous or weak, or that person lacks courage.
