It seems that most of the injuries that occur in badminton can be attributed to 2 main causes. The first is a lack of general physical preparation (GPP). This preparation is primarily for the bones, ligaments, tendons, and joints of the body. GPP makes way for specific physical preparation (SPP); muscles can be prepared in a relatively short period of time. Statistically, knees are the most frequently injured part of the body in badminton. The second cause is poor technique; as a friend of mine once informed me, tremendous relief can be had when one stops banging one's head off a wall. Poor technique can result from bio-mechanics as well as just doing it wrong.
Of course, the third and fourth are most probably old age and being overweight... oh man.
The physical load of badminton is primarily seen as an aerobic load by the body, even though many anaerobic demands are made. This is why aerobic training is so important for badminton. So, don't throw out the exercise bike just yet..