'Knees' in the Bible

Then she said, Here is my servant Bilhah, go in to her, so that she may have a child on my knees, and I may have a family by her.

Then Joseph took them from between his knees, and went down on his face to the earth.

And Joseph saw Ephraim's children of the third generation: and the children of Machir, the son of Manasseh, came to birth on Joseph's knees.