Comment by imzadi

It seems silly because a broken leg is obvious and easy to diagnose. So the idea that someone has an undiagnosed broken leg is absurd.

A lot of illnesses are not as easy to spot. Even illnesses that have clear diagnostic factors might be undiagnosed if no one has done the right tests. For instance, gallbladder disease. Easy to test and diagnose, but only if someone has gone to the doctor and the doctor has done the right tests. If you've experienced gallbladder disease, you know the symptoms. So you might start noticing them in other people who just think its indigestion or a pulled muscle or whatever.