The crusades effected medicine as a there was a lack of communication which was down to lack of trading as a result of fighting and war. Travel was more dangerous then it once was so there was less communication which meant places like Islam where thriving and slowly developing there knowledge in medicine whereas Europe was regressing and there understanding of medicine had been lost. An example of the extent of the regression is proved as at these times in Baghdad there where 60 hospitals whereas in London there was only one. Sorry if it wasn't of much help lol I'm only 14 :) xx