The avulsion fracture of the tibial attachment site of the anterior cr
uciate ligament is relatively rare among adults. Although partial avul
sion fracture of this site is very rare, complex forces exerted on the
knee joint could produce this type of fracture. We report on an adult
patient with an avulsion fracture of the attachment site of anteromed
ial bundle of the anterior cruciate ligament associated with injuries
of lateral and medial collateral ligament and fibular fracture. We spe
culate varus stress in a flexed knee coupled with rotation between the
femur and tibia caused this type of injury.