A force of knights on the flank would be more likely to break them. Risky for the knights, and a broken army will be hard to contain, but potentially great glory for the participants (and the leader who ordered it), as the leadership might be exposed.
So, it'll be a shorter battle, most likely, and pose the greatest risk to the knights. Overwhelming them will make it harder for the enemy to escape, but will likely bring greater casualties to your infantry, and the leadership would be more likely to escape.