Anterolateral rotatory instability is an excessive internal rotation of the tibia on the femur when the knee is bent, leading to excessive opening of the joint at the outer (lateral ) side.

-

An interpretation of a published medical article on the posteromedial corner of the knee.

-

The test for anterolateral rotatory instability is also called the 'Slocum Test'. Here is a video showing the Slocum test and embedded courtesy of 'HDAllDay21' -