How severe are initially undetected injuries to the knee accompanying a femoral shaft fracture?

Background: Fractures of the femur are severe injuries that quickly attract the physician's attention. Previous reports have shown that injuries to the ipsilateral knee can occur. In most cases, such injuries were diagnosed on delay. Excluding cases in which a knee injury was apparent already at admission, we sought to investigate the number and severity of initially undetected lesions to the knee concomitant with a femoral shaft fracture and give an overview of the literature referring to these combined injuries.
Methods: Charts and X-rays of patients treated for a femoral shaft fracture from January 2000 until December 2007 were reviewed. Patients, in whom any other injury of the affected limb apart from a midshaft femoral fracture was initially diagnosed, were excluded. Also patients, in whom an injury to the knee had been diagnosed at admission, were excluded.
Results: Fifty-three patients with 55 midshaft femoral fractures were available for analysis. An injury to the knee was diagnosed in three cases (5%). There was one partial tear of the posterior cruciate ligament and two grade two lesions of the medial meniscus. All lesions were conservatively treated without any after-effects.
Conclusion: Physical examinations under anesthesia, arthroscopy and magnetic resonance imaging have shown lesser correlation among each other than one would expect. More severe injuries to the knee with femoral shaft fractures are more likely to be detected early, than minor ones. Pain about the knee communicated by the awake patient should be the indication for further apparative examination by magnetic resonance imaging or arthroscopy.