What is the correct starting position of the knee in the pivot shift test?

The pivot shift test is used primarily to assess the integrity of the anterior cruciate ligament (ACL) within the knee. In this test, the starting position of the knee is crucial to correctly evaluating the ligament's stability.

In the pivot shift test, having the knee positioned in 30 degrees of extension is key as it allows for optimal loading and motion assessment during the test. This position effectively replicates the conditions under which an ACL injury is likely to cause a pivot shift phenomenon, specifically when there is a combination of valgus stress and internal rotation of the tibia relative to the femur.

Starting with the knee in full extension or flexion could compromise the effectiveness of the test. At full extension, the ACL is taut, potentially minimizing the knee's ability to demonstrate a pivot shift, while excessive flexion may alter the biomechanics and the movement patterns relevant to the test itself. Thus, the choice of 30 degrees of extension provides a balanced, athletic position that encourages appropriate movement patterns to reveal any instability linked to ACL insufficiency.