Quote Originally Posted by Orb
I can't really find any real situations of cavalry flanking in the medieval era. If anyone could dig some up, I'd be grateful.
I believe the battle of Nicopolis in 1396 was in the medieval era. It was decided, reportedly, by a flanking move of the Serb heavy cavalry (fighting on the side of the Ottomans) under Stefan Lazarevic.

Also, in the battle of Varna the Crusaders had an army composed primarily of heavy cavalry - the result of the battle is well known, and it only comes to prove that a cavalry charge is not all that it took in the Middle Ages to ensure victory. Heavy cavalry did have battle winning charge, but only if used properly - simply throwing it at the enemy did not work all the time.