A quick look at results from any road race over the last couple of years will almost certainly show an increase in the number of older runners when compared to 10 to 20 year ago.
Running injuries have always been around and unfortunately for some, plentiful. But, the changing demographic of runners competing has, according to a recent study - Running Injuries : Changing trends and demographics - has resulted in a change in the type of injuries being experienced, to those that tend to be experienced by 'Master' runners. Injuries such as achillies / calf injuries, illiotibial band injury and muscle injuries to the hamstrings and quadriceps.
As you would expect, the study suggests that running mileage and previous injury are important indicators of running injury. Therefore, the greater the current knowledge that is acquired about the changing demographics of runners and the application of research to treat injury offers hope that the number of injuries associated with long distance running can be reduced.