Posterior Drawer Test: Understanding Godfrey's Test, PCL Injuries, and Assessment

What is the other name for the posterior drawer test?

The posterior drawer test, a critical orthopedic assessment for knee stability, is also sometimes referred to as Godfrey's Test or Godfrey's Sign, particularly in older literature or specific clinical contexts.

Understanding the Posterior Drawer Test

The posterior drawer test is a fundamental clinical examination maneuver used to assess the integrity of the posterior cruciate ligament (PCL) of the knee. The PCL is one of the four major ligaments of the knee, playing a crucial role in preventing the tibia (shin bone) from moving too far backward relative to the femur (thigh bone). Injury to the PCL can significantly compromise knee stability and function, often resulting from direct trauma.

The Primary Alternative Name: Godfrey's Test

While "posterior drawer test" is the universally accepted and most common name, an alternative designation you might encounter is Godfrey's Test or Godfrey's Sign. This name is often attributed to the physician who described or popularized a specific method or observation related to PCL assessment. It is less frequently used in contemporary orthopedic and sports medicine literature compared to the descriptive "posterior drawer test," but it remains a historical and occasionally encountered reference, particularly when discussing the "sag sign" where the tibia appears to sag posteriorly when the knee is flexed.

Anatomy and Biomechanics of the PCL

The posterior cruciate ligament is the strongest and largest ligament in the knee. Originating from the lateral aspect of the medial femoral condyle and inserting into the posterior intercondylar area of the tibia, its primary function is to resist posterior translation of the tibia on the femur and to act as a secondary stabilizer against external rotation.

Mechanisms of PCL Injury:

• Direct Blow to the Anterior Tibia: Often seen in dashboard injuries during car accidents, where the flexed knee strikes the dashboard.
• Hyperextension Injury: Excessive straightening of the knee.
• Hyperflexion with Axial Load: Falling onto a flexed knee.

How the Posterior Drawer Test is Performed

The test is typically performed with the patient lying supine (on their back). The examiner flexes the patient's hip to 45 degrees and the knee to 90 degrees, with the foot flat on the examination table. The examiner then stabilizes the foot and places their thumbs over the anterior tibial plateau, applying a firm, posterior-directed force to the tibia.

Positive Finding: A positive posterior drawer test is indicated by excessive posterior translation of the tibia compared to the uninjured contralateral knee, often accompanied by a soft or absent endpoint. The degree of posterior translation is graded to assess the severity of the PCL injury.

Interpreting Results and Clinical Significance

A positive posterior drawer test strongly suggests a PCL tear or laxity. The clinical significance of this finding is profound, as PCL injuries can lead to:

• Chronic Knee Instability: Particularly during activities that involve knee flexion.
• Pain and Swelling: Especially in the acute phase.
• Functional Limitations: Difficulty with activities like descending stairs, squatting, or pivoting.
• Increased Risk of Osteoarthritis: Long-term instability can accelerate degenerative changes in the knee joint.

Accurate diagnosis is crucial for guiding appropriate management, which can range from conservative rehabilitation to surgical reconstruction, depending on the severity of the injury, patient activity level, and associated injuries.

Limitations and Considerations

While the posterior drawer test is highly sensitive and specific for PCL tears, it's essential to consider its limitations:

• Acute Pain and Swelling: Can make the test difficult to perform accurately or interpret.
• Associated Injuries: Other ligamentous or meniscal injuries can influence the test's findings.
• Chronic Laxity: In chronic PCL deficiency, the initial "sag" of the tibia (posterior sag sign) should be reduced before performing the drawer, to avoid misinterpreting the starting position.
• Examiner Experience: The reliability of the test can vary with the experience of the examiner.

For these reasons, the posterior drawer test is typically part of a comprehensive knee examination, often supplemented by other special tests (e.g., quadriceps active test, reverse pivot shift test) and diagnostic imaging such as Magnetic Resonance Imaging (MRI) for definitive diagnosis.

Conclusion

The posterior drawer test is a cornerstone in the clinical assessment of posterior cruciate ligament integrity. While its primary and most recognized name is descriptive of its action, understanding its alternative designation as Godfrey's Test enriches one's knowledge of orthopedic terminology. Regardless of the name used, the test remains an indispensable tool for clinicians in diagnosing PCL injuries and guiding effective patient care, emphasizing the importance of thorough clinical examination in conjunction with advanced diagnostic modalities.