Genesis 50:23

‘And Joseph saw Ephraim's children of the third generation. The children also of Machir, the son of Manasseh were born on Joseph's knees.'

That he lives to a grand old age is certain, for he lives to see his great, great grandsons.

“Born on Joseph” s knees.' That is were placed on his knees at birth as the proud grandfather. Among the Semites the placing on the knees was an important indication of acceptance. This is possibly what is in mind in Job 3:12 where we read ‘why did the knees receive me?'. When a child was adopted it was ‘placed on the knees' (see on Genesis 48:11).