Writers are always looking for information about their characters' injuries and how to treat them. I just ran across a book that looks like a great resource for learning about medieval military medicine. Piers D. Mitchell's
Medicine in the Crusades: Warfare, Wounds and the Medieval Surgeon discusses the types of injuries that occurred during the campaigns of the twelfth and thirteenth centuries in the Middle East and the ways that medieval surgeons dealt with them.
In recent years scholars have been discovering that medieval medicine was more sophisticated than they originally assumed. This book challenges some of the older assumptions about the state of European medical knowledge at the time.
Another article on the subject is Linda M. Paterson's "
Military Surgery: Knights, Sergeants and Raimon of Avignon's version of the Chirugia of Roger of Salerno (1180-1209)". Sadly the version on Google Books has the first sixteen pages cut out.
The article beyond the image link claims that this picture from Roger of Salerno's Chirugia is a treatment for spinal curvature, but the text of the medieval manuscript (quoted in Paterson at
pp. 141-142) says it's the resetting of a dislocated shoulder.