How to perform the stutter test
The patient sits on the edge of the examination couch with both legs hanging over the edge at 90 degrees. The examiner sits to the one side of the knee and places a finger over the medial side of the knee. The patient is asked to slowly straighten the knee and the examiner feels for a 'stutter' in the joint at about 45-60 degrees of flexion. This is the posisiton where an enlarged plica might impinge between the femur and the patella.
Synovial Plica Syndrome of the Knee: A Commonly Overlooked Cause of Anterior Knee Pain. Lee PYF, Nixion A, Chandratreya A and Murray JM. Surg J (N Y). 2017 Jan; 3(1): e9–e16.