The Active External Rotation Sign: A Physical Exam Technique for Detecting Posterolateral Corner Injury in Chronic...

Area of Science:

• Orthopedic Surgery
• Sports Medicine
• Knee Biomechanics

Background:

• The posterolateral corner (PLC) is crucial for knee stability, comprising multiple ligaments and tendons.
• PLC injuries are often overlooked due to complex anatomy and diagnostic challenges.
• Untreated PLC lesions lead to significant knee instability and poor functional outcomes, necessitating surgical intervention.

Purpose of the Study:

• To introduce and demonstrate the "active external rotation sign" as a novel clinical diagnostic tool.
• To describe a new method for identifying chronic posterolateral corner injuries.

Main Methods:

• The "active external rotation sign" involves patients with suspected PLC deficiency actively contracting hamstrings at 90° knee flexion.
• This action elicits dynamic external tibial rotation and posterior translation, indicative of PLC incompetence.
• The test utilizes active patient motion, contrasting with passive stress tests.

Main Results:

• The active external rotation sign demonstrates abnormal and asymmetric knee motion in patients with chronic PLC injuries.
• This sign reflects the biomechanical consequences of PLC deficiency, similar to the dial test but with active muscle contraction.
• The observed motion is due to the unopposed pull of the biceps femoris on the fibula without PLC stabilization.

Conclusions:

• The active external rotation sign is a valuable clinical indicator of posterolateral corner (PLC) injury.
• Early and accurate detection of PLC injuries is essential for successful surgical management.
• Addressing PLC incompetence concurrently with cruciate ligament reconstruction prevents potential surgical failure.