BackgroundConcomitant knee injury is a common finding in femoral fractures but can be easily missed during early management of the initial trauma. Degrees of damage to the articular structures vary considerably; from only a mild effusion to complete ligamentous and meniscal tears. Since previous reports were mostly from developed societies, this study was designed to look into characteristics of associated knee injury in a sample from Iran, to represent a developing country perspective.Materials and methodsConsecutive patients admitted to an orthopedic ward of Baqiyatallah hospital (Tehran, Iran) with diagnosis of femoral fracture were enrolled in this study between October 2008 and September 2009. In patients who met the inclusion criteria of the study, arthroscopic or open surgical examination of the knee, ADT, Lachman test, varus and valgus stress tests under anesthesia were carried out to determine the incidence of knee injury.ResultsForty patients with ipsilateral and two patients with bilateral femoral fractures were studied. Arthroscopy revealed medial meniscus injury in 12 (27 %) knees. Three (7 %) lateral meniscus injuries, 18 (40.9 %) ACL injuries and 2 (4.5 %) PCL injuries were also found. In varus and valgus stress tests, 15 (34 %) MCL and 4 (9 %) LCL laxities were noticed. The Lachman test was positive in 3 (6 %), and ADT was positive in 2 (4.5 %) patients.ConclusionsBased on our observations, concomitant ligamentous and meniscal knee injury is a common finding in femoral shaft fractures and rates of these injuries are generally in concert with reports from developed nations.