As a general rule, plain films are insensitive in ruling out orthopedic injuries. One particularly tricky area is the knee. This 2-view knee series above is normal.
Did you know that the sensitivity of picking up knee fractures is as low as 79% with a 2-view series and 85% with a 4-view series? With the advent of CT imaging, more and more subtle fractures are being found.
Here is the same patient with 2 oblique views:
Although oblique views add more sensitivity in detecting fractures, these are also normal. However in the CT reformats of this patient's knee, the fracture becomes obvious - a depressed lateral tibial plateau fracture.