Posterior Drawer Test and Posterior Sag Sign (Godfrey Test): PCL Tear Guide
In short
Dashboard injuries and hyperflexion trauma frequently rupture the Posterior Cruciate Ligament (PCL). Learn how the Posterior Drawer test and Godfrey Posterior Sag sign accurately grade PCL laxity.
In this guide (8 sections)
Anatomy and Mechanics of the PCL
The Posterior Cruciate Ligament (PCL) is the primary stabilizer against posterior translation of the tibia relative to the femur, resisting 95 percent of posterior displacing forces.
PCL injuries occur typically during motor vehicle dashboard impacts (where the flexed tibia hits the dashboard) or athletic falls directly onto a flexed knee with the foot plantarflexed.
The Posterior Sag Sign (Godfrey Test)
Before touching the patient knee, observe the resting profile from the side:
- Setup: The patient lies supine with both hips and knees flexed to 90 degrees, heels resting flat on the table.
- Observation: The clinician views both tibial profiles horizontally from the side.
- Positive Finding: In an injured PCL, gravity pulls the proximal tibia backward, creating a visible concavity or step-off beneath the patella compared to the normal knee.
The Posterior Drawer Test Protocol
With the knee flexed to 90 degrees and the patient foot stabilized, the clinician pushes the proximal tibia directly backward. Grading is determined by the relationship between the anterior tibial plateau and the femoral condyles:
Grade I: 0 to 5 mm posterior translation (tibial plateau remains anterior to femoral condyles); Grade II: 6 to 10 mm translation (tibial plateau flush with femoral condyles); Grade III: >10 mm translation (tibial plateau subluxates posterior to condyles, indicating combined PCL and posterolateral corner tear).
Diagnostic Accuracy Table
| Examination Test | Sensitivity | Specificity | Clinical Role | |
|---|---|---|---|---|
| Posterior Drawer Test | 90 percent | 99 percent | Gold standard physical examination test for PCL tears | |
| Posterior Sag Sign (Godfrey) | 79 percent | 100 percent | Highly specific visual screening maneuver | |
| Quadriceps Active Test | 54 to 98 percent | 98 to 100 percent | Confirms active reduction of posterior tibial subluxation |
Frequently Asked Questions
How can a PCL tear cause a false-positive anterior drawer test?
When a torn PCL allows the tibia to sag backward, pulling the tibia forward simply restores normal resting position. A clinician unaware of the posterior sag may mistake this forward movement for an ACL tear.
Do isolated Grade I and II PCL tears require surgery?
No. Isolated Grade I and II PCL tears have excellent biological healing potential and are managed non-operatively with quadriceps-strengthening rehabilitation and dynamic PCL braces.
Posterior Cruciate Ligament Bundles and Injury Mechanics
The PCL consists of a robust anterolateral bundle (taut in flexion) and a posteromedial bundle (taut in extension). It is twice as thick as the ACL and primarily restrains posterior translation of the tibia. Classic injury mechanisms include direct impact to the flexed proximal tibia (dashboard injury) or falling heavily onto a flexed knee with the foot plantarflexed.
Quadriceps-Dominant Rehabilitation Protocol
Conservative management yields excellent functional recovery for Grade I and II PCL tears. Rehabilitation focuses on intense quadriceps strengthening (straight leg raises, terminal knee extensions, leg presses from 0 to 45 degrees) because the quadriceps acts as an active antagonist to posterior tibial displacement. Isolated hamstring curls are strictly prohibited for 8 weeks.
Two-Wheeler Accidents in Indian Traffic
Motorcycle and scooter collisions where the rider knee impacts the front fairing or road surface are the predominant cause of PCL tears in India. Prompt clinical diagnosis prevents chronic patellofemoral joint overload and secondary medial compartment arthritis.
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