To better understand anatomic and other possible predisposing factors for anterior cruciate ligament injuries, we retrospectively studied 31 patients with noncontact, bilateral injuries of this ligament. The 31 patients were carefully matched by age, sex, height, weight, and activity level with 23 control subjects who had no history of knee injury. All 54 subjects underwent a full clinical knee examination, joint hypermobility tests, a hamstring tightness assessment, a computerized tomography scan analysis, and a plain view radiographic analysis, and were asked to provide a complete immediate-family history of knee ligament injury. In addition, the 31 patients in the experimental group underwent a KT-1000 arthrometer knee laxity examination and were also asked to provide an injury profile, including mechanism of injury, treatment received for each injury, and the time interval between injuries. Measurements obtained from the computerized tomography scan analysis demonstrated a significantly wider lateral femoral condyle in the experimental group compared with the control group, indicating that certain anatomic factors may predispose people to anterior cruciate ligament injury. A significant difference was also found in the incidence rate of anterior cruciate ligament injury in the family history of the experimental group compared with the control group, indicating a possible congenital aspect of this injury.