Explain the anterior and posterior drawer signs of the knee

Discussion in 'USMLE STEP 2 CS' started by Rex, Sep 13, 2005.

  1. Rex

    Rex Guest

    explain the anterior and posterior drawer signs of the knee joint?

    Ant drawer sign:
    position:supine,hip flex 45 ,flex knee 90 then manage the position of knee joint ( neutral , int rotate , ext rotate ) depend on what ligament you want to test the laxity
    exam:locate tibial plateu which should be anterior to femoral condyle
    7 mm (if it is posterior then the PCL laxity is suspected)
    put your thumbs at tibial plateau and fingers at hamstring (to see
    is there is any spasm which results in false negative 54% in acute injury)
    pull tibia excessively fowards on femur if it move more than 3mm then ADS positive(the ACL laxity did not function to prevent the tibia to move forward)
    neutral position : test ACL
    internal rotation :test ACL and lateral ligament of PCL
    external rotation:test ACL and MCL AND post-medial capsule
    POST drawer sign:
    same position ADS
    first notice if there's any drop back of tibia
    If yes you have to pull the tibia forward so you will know there' firm end that means ACL intact
    Then if you can push tibia excessively then there' s PCL laxity

    By the way the ADS(ant drawer sign) can cause false negative in acute injury so Torg(1976) suggest Lachman test that sensitivity in both acute and chronic phase 99%
    Lachman test:flex knee20-30 one hand hold proximal tibia and pull anterior while the other hand fix distal femur ,observe if there's any excursion end point sulcus or slope patella

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