When most laypeople think of a knight they think of the "golden age" of knighthood: a man clad in plate armour upon a high backed saddle on a destrier, his feet in saddles whilst he keeps up the tenants of the chivalric code. The problem I have is that the most famous knights in my opinion (king Arthur's knights of the round and Charlemagne's paladins) existed centuries (up to a millennia) before these things were invented.
My question is what these two core groups of famous knights looked like (what they wore, what they rode, how the fought) and did they have any non-revisionist tenets of action? Would King Arthur's "knights" been more like Alexander's sacred band?
So, the issue I'm having with trying to answer this question is that both Charlemagne's paladins and Arthur's knights are essentially literary, rather than historical, figures. Both sets of characters originated in iconic works of high medieval literature: the Arthur legend first took real shape in Geoffrey of Monmouth's The History of the Kings of Britain, while Roland and the paladins come to us from the aptly titled Song of Roland. Both date from the early 12th century, but purport to describe events which happened hundreds of years earlier. The Song of Roland has a kernel of truth to it, in that Charlemagne campaigned briefly in Spain, though at a greatly diminished scale and scope, and his rearguard was attacked (by Basques, not Muslims!) while the army was passing through the Pyrenees back into France. But the Arthur legend is, if not totally fictional, then at least mostly so. If there was such a British war leader, we have no contemporary evidence for his existence.
Halsall, Guy. Worlds of Arthur: Facts and Fictions of the Dark Ages.