To avoid a similar number of cruciate ligament injuries boys would have to exercise for even longer, for they are not so susceptible to such injuries in the first place.
Curiously, the exercises did not protect against other knee injuries deemed to be serious, of which there were 19 in the exercise group and 17 in the control group. Nor was the overall rate of acute injury of the knee (serious and non-serious) reduced: it was 48 in the exercise group and 44 in the control group.
Assuming what may not be entirely true, that knee injuries are randomly distributed in the population of female adolescent soccer players (that is to say they do not have individual differences in their susceptibility to them), the chances of an adolescent female soccer player suffering an acute knee injury over five seasons is about 10 percent, and slightly more than 5 percent for a serious knee injury. This is a very high risk: it is even possible that drivers who habitually drive while over the limit get away with it more often than that.
Of course, drunk drivers injure people other than themselves, but so do soccer players. It is, after all, in tackles that most cruciate ligament injuries on the field occur; and while it is true that soccer injuries very rarely kill, a cruciate ligament injury can lead to a lifetime of pain.
The case for banning adolescent female soccer on grounds of health and safety, then, is clear, especially in those countries in which, unlike Sweden, there is no doctor or physiotherapist on call to treat the injured. What other activity would be tolerated that had so high a risk of painful or serious injury? And what is true of soccer is true of virtually all sports, so many of which end in pain and injury. In a world in which thousands of children die of diarrhoeal diseases, why should so many medical resources be diverted to treating what are, after all, self-inflicted injuries?