The area affected by anterolateral rotatory instability is the region at the front of the knee on the outer side.
What is the significance of anterolateral rotatory instability?
The finding of anterolateral rotatory instability implies damage to the anterior cruciate also involving one or several other structures:
"....Rotatory instability of the knee represents the main reason for failure and poor clinical outcomes regarding anterior cruciate ligament (ACL) reconstruction techniques. It is now clear that the anterolateral complex (ALC) of the knee possesses a fundamental role, in association with the ACL, in controlling internal rotation...."
Other relevant links -
Anterior cruciate ligament, Anterolateral ligament, Iliotibial band, Lateral meniscus, Capsule