The figure-4 test is performed in patients who may have tears of their popliteomeniscal fascicles to the lateral meniscus. These patients commonly present with vague lateral knee pain and often do not have any findings on the MRI scans to indicate a lateral menicus tear. The way that this test works it that the popliteus tendon normally pulls the meniscus out of the joint when the knee is brought into a figure-of-4 position. However, when the popliteomeniscal fascicles are torn, the meniscus will sublux back into the joint and becomes pinched. This most commonly occurs in wrestlers.
Performance of the figure -4 test is performed by having the patient place the foot of the affected extremity on the contralateral knee. For a right knee, this resembles the number “4”. A positive test which reproduces their symptoms over the lateral joint line is suspicious for either a peripheral meniscal tear or a tear of the popliteomeniscal fascicles. Further testing may be indicated to include an MRI scan and probing of the lateral meniscus during arthroscopy to make sure this is the source of the pain.