'Knees' in the Bible

All hands shall be feeble, and all knees shall be weak as water.

And it shall be, when they say unto thee, Wherefore sighest thou? that thou shalt answer, For the tidings; because it cometh: and every heart shall melt, and all hands shall be feeble, and every spirit shall faint, and all knees shall be weak as water: behold, it cometh, and shall be brought to pass, saith the Lord GOD.

Again he measured a thousand, and brought me through the waters; the waters were to the knees. Again he measured a thousand, and brought me through; the waters were to the loins.