In forty fresh human cadaver knees the function of the anterior cruciate
ligament and of its two component parts, the posterolateral part and the
anteromedial band, were studied by cutting these ligaments and others in
different sequences and combinations and then manually stressing the knees.
The anterior drawer sign cannot be obtained unless the anteromedial band is
severed. The postolateral part and the medial collateral ligament are,
respectively, the secondary and tertiary restraints limiting the anterior
drawer sign. Both internal and external rotation are limited by the
anterior cruciate ligament, especially when the knee is in extension. The
anterior cruciate ligament also limits hyperextension.