Heavy cavalry charges used to demolish any infantry line they could find, it was basically a squad of elite warriors whose sole occupation was war since the age of 12-14 against a swarm of lightly armored undertrained, underfed and undersized(nobles were on average much taller and stronger than the rest of the population at those times because of their far superior protein intake) peasants whose bodies barely functioned from all that "13houradayfarmwork" life they had to go through.
Even after the pike formations were set on the battlefield the knights only became heavier with armor and coated their horses in plate which caused them to wreak havoc until mass firearms were introduced mid 16th century.
Just look at this guys biography;
http://en.wikipedia.org/wiki/Pierre_...neur_de_Bayard
1503 - Battle of Garigliano;
"At the Battle of Garigliano he single-handedly defended the bridge of the Garigliano against 200 Spaniards, an exploit that brought him such renown that Pope Julius II tried unsuccessfully to entice him into his service."
- 1508;
"a breakneck cavalry charge up a mountain slope against a seemingly impregnable barricade, defended by a pike-phalanx of Genoese militia. The Genoese shattered and fled before the furious charge of Bayard and the French gendarmes. Genoa subsequently fell, and Bayard entered the city in triumph behind his king.
That's right, they charged this;
http://img534.imageshack.us/img534/1...naferremar.jpg
...uphill against a heavily fortified position and obliterated the entire unit barely loosing any men...
Those stories everyone keeps blabbing about of heroes stopping heavy cavalry charges are just boasted tales that happened a couple times in a course of tens of centuries in between which you had a hundred cases of cavalry flatting entire armies to the ground for every one of those "look at me I am an underdog, look at me how I stick it up to the Man" tales of ordinary people facing and defeating their brutal overlords which has become such a popular theme lately.