Psd test in ortho
The Posterior Sag (Drawer) Test - also called the Posterior Sag Sign or Gravity Drawer Test - is used in orthopedics to assess posterior cruciate ligament (PCL) integrity in the knee.
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Here is a complete overview of the Posterior Sag (Draw) Test in orthopedics - a key clinical test for Posterior Cruciate Ligament (PCL) injury:
Posterior Sag Test / Posterior Drawer Test - PCL Assessment
What it Tests
Both tests assess integrity of the Posterior Cruciate Ligament (PCL), the primary restraint to posterior tibial translation between 30° and 90° of knee flexion.
1. Posterior Sag Sign Test
Position: Patient supine; a pillow is placed under the distal thigh while the heel rests on the stretcher.
Angle: Knee flexed to 45° or 90°.
Positive finding: The tibia visibly sags (drops) backward on the femur - indicates PCL insufficiency.
Sensitivity: ~79% in the acute phase.
Important note: A false-positive anterior drawer test can occur if the examiner misses the posterior sag sign - the tibia translates forward from its already-posteriorly displaced position, mimicking an anterior drawer.
2. Posterior Drawer Test
The most reliable clinical test for PCL injury.
Position: Patient supine, knee flexed to 90°, foot stabilized by examiner.
Maneuver: Apply a smooth, firm backward (posterior) force to the anterior aspect of the proximal tibia / tibial tubercle.
Positive finding:
- Posterior tibial displacement > 5 mm, or
- A soft/absent end point
Sensitivity: ~85% in PCL-insufficient knees (55% in some ED series).
Grading of laxity:
| Grade | Displacement |
|---|---|
| Grade I | 0-5 mm |
| Grade II | 5-10 mm |
| Grade III | >10 mm |
If >10 mm of posterior translation is noted at 30° and/or 90°, a combined PCL + posterolateral corner injury must be suspected.
Clinical Pitfall
Always compare with the contralateral (normal) knee - baseline ligamentous laxity varies between patients. The PCL injury may also occur alongside other ligamentous injuries, especially in high-energy trauma.
Mechanism of PCL Injury
- Anterior-to-posterior force applied to the tibia (e.g., dashboard injury)
- Hyperextension of the knee
- Direct blow to a bent knee
Sources: Rosen's Emergency Medicine; Tintinalli's Emergency Medicine; Bailey and Love's Short Practice of Surgery, 28th Ed; Campbell's Operative Orthopaedics, 15th Ed 2026
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