Avulsion of the femoral attachment of the anterior cruciate ligament in a 3-year-old boy.

The incidence of anterior cruciate ligament injury is rare in children. Deficient or absent cruciate ligaments have previously been described as the cause for congenital dislocation of the knee in newborns. We report a case of a 3-year-old boy who presented with a swollen left knee, which did not resolve over a 10-day period. He would not bear weight or extend the knee beyond 45 degrees, and had significant pain with passive extension. Arthroscopy revealed an anterior cruciate ligament that appeared to have been sheared off its attachment to the lateral femoral condyle. This is the youngest patient reported with traumatic disruption of the anterior cruciate ligament.