Anterior stability testing is performed primarily to assess the integrity of the anterior cruciate ligament (ACL). The ACL is the main stabilizer to anterior translation of the knee between 20°-30° of knee flexion. For this reason, the majority of knee stability testing for the ACL is performed at this angle. In addition, the ACL is important for anterolateral rotatory stability of the knee, so the “pivot shift” test is also an important part of this examination.