The locomotive misconception in regards to plate armor likely comes from a combination of sources. First, we gather that mounted armored fighters were the minority in a military force, and they were usually surrounded and supported by others (pikemen, archers, footmen, handgunners), giving the impression of needing assistance. In group combat, all participants have a role, but if the knight (not all knights were warriors, some folks could be knighted for rendering other services) is alone with the opponent, the armor's mobility should provide him with the necessary adjustments. Furthermore, consider that these plates were tailored specifically for the wearer, so all measurements were customized. As cities grew, militia men, mercenaries and lower nobility would compile bits and pieces as loot or even purchased at fairs. So while a man of lower social status might own say, a pauldron, his helmet might belong to an entirely different set. This does not preclude the possibility of altering armor to fit a new wearer. Secondly, armor weighs less than a fireman's equipment (about 25 kilograms) and, with all the leather straps, riveting and interlocking plates, it acts more like the exoskeleton of a lobster. In regards to the myth of immobility, we can point to films depicting mounted knights. Other than that, a little studying of the object in question, and observing them in a museum can provide insight to their utilization in a field of battle. Kindly visit the Metropolitan Museum of Art's website for lovely pictures. http://www.metmuseum.org/collection/the-collection-online/search?&noqs=true&ft=*&when=A.D.+1400-1600&deptids=4&pg=1

Breiding, Dirk H. "Arms and Armor—Common Misconceptions and Frequently Asked Questions". In Heilbrunn Timeline of Art History. New York: The Metropolitan Museum of Art, 2000–. http://www.metmuseum.org/toah/hd/aams/hd_aams.htm (October 2004)