Corrected entry: In the first jousting scene after William is given his new armor from Kate, Roland and Wat lie to him about his next opponent having raised his country's taxes to pay for the tournament and then cut to a shot of his opponent trying to mount his horse. The problem is he mounts the horse from the wrong side. The knight should have mounted from the left side but can plainly be seen mounting from the right. Mounting from the left is an equine tradition dating back to the times of knights and is done because the sheath of a sword is worn on the left and gets in the way if they try to mount from the right. Surely a knight would have known this.
Corrected entry: When William is facing Adhemar in the final match, Adhemar almost destroys Williams' frontal armor's right side (you can even see it is folded in two). When they are preparing for the second round his armor is intact again. When the second round begins, back to the destroyed armor. (01:58:20)
Corrected entry: When Heath and his crew are entering into the World Championships, we hear the crowd begin to chant Ulrich's name, but if you look at the crowd in the background, they are simply yelling, and their mouths are not in sync with the chanting at all.
Corrected entry: When knights jousted, they would only ride on the left-hand side of the barrier as it was easier to hit their opponent. In this film, they only seem to right ride on the right-hand side of the barrier.
Corrected entry: During the last joust of the movie William is injured but when the joust is finished he hops right over the fence using his injured arm as support, and appears unaffected by the injury.
Corrected entry: At the end of the last jousting scene, William is stabbed in the shoulder with a lance, but there's no hole in his shirt, only blood.
Corrected entry: In the opening sequence when the captions come up "In medieval times, a new sport emerged...", we see a knight being knocked off his horse in a joust. The knight being knocked off is wearing Heath Ledger's original suit of armor. (You can tell by the shield he is holding - it has the three phoenixes on it.)