Kitzur 1:3 says אך בשעת הדחק די עד קשרי אצבעותיו,
Could you please clarify which knuckles and if the knuckles themselves shouls be washed>
The knuckles are the points at which the fingers connect with the hand.
The idea is that although it is best to wash the entire hand, if one is short of water it is sufficient to wash the fingers alone – fingers being defined from the knuckles and down. One should wash until the end of the knuckles, which is the wording used by some of the Poskim.
See for instance the laws of Yom Kippur, Orach Chaim 613:2, which mentions “the end of the knuckles”; the Magen Avraham proves from here that it is sufficient to wash the fingers, and the fingers continue until the knuckles.