Posterior Sag Sign

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 Posterior Sag Sign


What is 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.

How do you do Posterior Sag Sign?

Posterior Sag Sign
Posterior Sag Sign

What does a positive Posterior Sag Sign mean?

Sensitivity & Specificity

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

Notes

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




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