ok, I think I understand the problem - you need to insert a bone between the ones that are already there. or - you have joint 1 & 3 connected and need to put in #2 so that you have a 1-2-3 connection, not a 1-3-2 or two separtate connections of 1-2 & 1-3. if I'm right about that, then the fix is... (drum roll please) select the bone shown in your image that is between the green crosshairs and the red circle (the hand I suppose) create the missing bone (you can adjust this later) now select one of the bones that is supposed to be attached at the other end, go to the file menu and select Object-Change Parent and have it point to the newly created missing bone, repeat as needed.