Posterior Sag Sign (or Gravity Drawer Test) is used to assess the integrity of the posterior cruciate ligament of knee (PCL tears). It’s also called Godfrey Sign.
How it’s Performed?
The patient lies in the supine position with the hips flexed at 45° and knees flexed at 90°.
The clinician assesses the contour of the tibial tuberosities.
What does a positive Posterior Sag Sign mean?
Positive sign when the affected tibia sags posteriorly compared to the unaffected knee.
If there is a rupture (partial) of the PCL, the tibial tuberosity on the involved side will be less visible than that on the noninvolved side.
This discrepancy is caused by an abnormal posterior translation, resulting from a rupture of the PCL.
Sensitivity & Specificity
Sensitivity: 79 %
Specificity: 100 %
In cases of doubt, the patient can be asked to contract the hamstrings slightly by pushing the heels into the clinician’s arm. This maneuver usually results in an increase in the posterior translation of the tibia and is often performed as a quick test of the integrity of the PCL.
Posterior sag sign can be shown by passive elevation of the leg in a fully extended position of knee, with the examiner applying the elevating force at the ankle. The test is interpreted as positive sag sign, if the tibia falls back on the femur in case of PCL insufficiency
Rubinstein RA Jr, Shelbourne KD, McCarroll JR, VanMeter CD, Rettig AC. The accuracy of the clinical examination in the setting of posterior cruciate ligament injuries. Am J Sports Med. 1994 Jul-Aug;22(4):550-7. doi: 10.1177/036354659402200419. PMID: 7943523.
Clinical Tests for the Musculoskeletal System, Third Edition book.
Mark Dutton, Pt . Dutton’s Orthopaedic Examination, Evaluation, And Intervention, 3rd Edition Book.