This is going to be a video on the posterior sag sign also called gravity drawer test for PCL failure.
To perform this test have your patient in supine lying position
with his hips flexed to 45 degrees and the knees flexed to 90 degrees.
In this position the tibia drops or sags back posteriorly on the femur due to gravity
if the PCL is torn.
Normally the tibial plateau
extends one centimeter anteriorly beyond the femoral condyle
like seen in this case.
So if you were to see a concavity distal to the patella,
we are talking about a positive posterior sag sign.
If you observe a positive posterior sag sign
your patient should slowly extend his knee
while you fixate the hip in 90 to 100 degrees of flexion.
This action is sometimes called the voluntary anterior drawer
and its results are comparable to that of the anterior drawer test.
As the patient does this
the tibial plateau will shift back forward to its normal position,
indicating that it was subluxed on the femur previously.
With a positive posterior sag sign
you should be aware that the anterior drawer test and the Lachman test
could give you a false positive result
as the movement of the tibia will be increased.
Alright,
this was our video on the posterior sag sign.
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and if you want to learn another way on how to assess for PCL tear
check out our posterior drawer test video right here
or if you want to learn how to assess an ACL tear
check out our anterior drawer video right here.
I'll catch you next time, bye!