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Special Test

Posterior Sag Sign


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.

See Also: Posterior Drawer Test of the Knee

How do you do Posterior Sag Sign?

  • The patient lies in the supine position with the knees flexed to approximately 90 degrees and the legs supported under the lower calf/ heel by the clinician’s arm.
  • The clinician assesses the contour of the tibial tuberosities.
Posterior Sag Sign
Posterior Sag Sign

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.
See Also: Quadriceps Active Test

Sensitivity & Specificity

This test may have some value as a screening test when negative due to its high sensitivity:

  • Sensitivity: 79 %
  • Specificity: 100 %

Notes

  • 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

Gravity Sign and Genu Recurvatum Test

The patient lies supine with the hip and knee of the affected leg flexed 90°. With one hand, the examiner grasps the patient’s lower leg while stabilizing the knee proximal to the patella with the other hand. The examiner then abruptly pulls away the stabilizing hand from the knee.

If the posterior cruciate ligament is torn, the tibia will recede posteriorly (posterior droop).

In the genu recurvatum test, the extended leg is lifted. A torn posterior cruciate ligament will result in a posterior drop of the tibia.

Gravity Sign
Posterior drop of the tibia after removal of stabilization

Quadriceps Contraction Test

Quadriceps Contraction Test is a similar test used to assess the posterior cruciate ligament injury.

The patient is supine. The injured leg is flexed 90° at the knee and placed in external rotation. The patient is asked to tense the quadriceps and lift the leg on the examining table.

In the presence of posterolateral instability, the external rotation of the foot causes posterior subluxation of the lateral tibia relative to the lateral femoral condyle. The examiner observes this as a posterior drop of the lateral tibial plateau. The active quadriceps contraction and increasing knee extension cause the lateral tibial plateau to move anteriorly out of posterior subluxation and into reduction with a sort of reverse pivot shift. The joint reduces at about 30 to 20° of flexion. This test is also called an active reduction test and can usually be demonstrated only in the presence of chronic ligament injuries.

Quadriceps Contraction Test
Quadriceps contraction test. (a) Subluxation with posterior drop. (b) Tensing the quadriceps. (c) Active knee extension: reduction position.

Reference

  • 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.
  • Fowler PJ, Messieh SS. Isolated posterior cruciate ligament injuries in athletes. Am J Sports Med. 1987 Nov-Dec;15(6):553-7. doi: 10.1177/036354658701500606. PMID: 3425783.
  • Clendenin MB, DeLee JC, Heckman JD. Interstitial tears of the posterior cruciate ligament of the knee. Orthopedics. 1980 Aug 1;3(8):764-72. doi: 10.3928/0147-7447-19800801-07. PMID: 24822488.
  • Clinical Tests for the Musculoskeletal System, Third Edition book.
  • Mark Dutton, Pt . Dutton’s Orthopaedic Examination, Evaluation, And Intervention, 3rd Edition Book.
Last Reviewed
May 24, 2022
Contributed by
OrthoFixar

Orthofixar does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice.

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