Diagnostic imaging in a patient with an acute knee injury.

The patient was a 23-year-old man, currently serving in a military airborne operations unit. During a jump training exercise, the patient's right lower extremity became entangled in his parachute equipment upon exiting the aircraft, which caused hyperextension and valgus forces upon his right knee. Due to concern for a fracture, the patient was transported to an emergency department, where conventional radiographs were completed and interpreted by a radiologist as negative for a fracture. Following further physical examination by a physical therapist, magnetic resonance imaging of the right knee was ordered, revealing ruptures of the anterior cruciate ligament and medial collateral ligament.