Posterolateral Corner Knee Injury

Posterolateral corner injuries are often associated with significant trauma and can occur in isolation or, more commonly, in conjunction with other knee injuries. The causes of PLC injuries can be categorized into several key areas:

• Traumatic Causes: Sports Injuries, Motor Vehicle Accidents, Falls
• Non-Traumatic Causes: Degenerative Changes, Repetitive Stress

• Instability – the knee will feel unstable when turning or pivoting.
• There will be mild swelling outside the knee, generally not associated with intra-articular joint swelling unless an accompanying injury occurs.
• Numbness along the outside of the knee or drop foot can occur from peroneal nerve injuries, which are associated with PLC injuries.

Knee surgeon Dr. Daniel Kaplan will diagnose posterolateral corner injuries based on physical exam and imaging. A specific physical exam test is the varus stress test – bending the knee and stressing the ligaments of the PLC. The dial test assesses knee rotation at thirty degrees and ninety degrees; this can help differentiate whether the posterior cruciate ligament is injured with the PLC. Many of the exam maneuvers will also assess the cruciate ligaments (anterior cruciate ligament and posterior cruciate ligaments), as these are injured in approximately 72% of patients with a PLC injury.

• Grade I Injury: small partial tear with minimal instability
• Grade II Injury: partial tear with an endpoint to stressing
• Grade III Injury: complete tear with no good endpoint to stressing