The posterolateral corner (PLC) is a group of structures on the back and outside of the knee that resist lateral rotation and varus stress. PLC injuries are uncommon in isolation and are most often associated with ACL or PCL injuries. Missed PLC injuries are a leading cause of failed cruciate ligament reconstruction, which is why recognition and treatment of PLC pathology is central to multi-ligament knee care.
What Is a Posterolateral Corner Injury?
The PLC includes the lateral collateral ligament (LCL), the popliteus tendon and muscle, the popliteofibular ligament, the arcuate ligament, and the posterolateral capsule. Together these structures:
- Resist varus force (a force pushing the knee outward)
- Control external rotation of the tibia
- Provide secondary restraint to posterior translation
PLC injuries are graded:
- Grade I: stretch injury with some tenderness and minor laxity
- Grade II: partial tear with increased laxity but a firm endpoint
- Grade III: complete tear with significant laxity and no firm endpoint
Isolated PLC injuries are uncommon and tend to do poorly when missed. Associated ACL or PCL injuries, which occur in the majority of PLC cases, magnify the functional consequences of unrecognized PLC pathology.
Causes and Risk Factors
- Direct blow to the medial side of the knee (varus force)
- Hyperextension injuries with rotation
- Knee dislocation
- Motor vehicle collisions
- Contact sports with associated pivot or twist
- Concomitant ACL or PCL tear raises the index of suspicion
Symptoms
- Pain on the outside and back of the knee
- Instability with pivoting or walking on uneven ground
- Feet-out feeling (external rotation of the tibia) when turning
- Peroneal nerve symptoms in some cases: foot drop, numbness on the outside of the lower leg
- Combined symptoms with associated ACL or PCL injury (giving-way, difficulty with stairs)
Diagnosis
Dr. Chudik’s evaluation includes the mechanism and a physical examination with PLC-specific tests: varus stress testing at 0 and 30 degrees (pure LCL versus combined posterolateral laxity), dial test (external rotation asymmetry at 30 and 90 degrees of flexion), and posterolateral drawer. Peroneal nerve examination is documented. X-rays rule out associated fractures, including the arcuate fracture (a small avulsion fragment at the fibular head that is pathognomonic for PLC injury). MRI confirms the specific structures torn and characterizes associated injuries. The Westmont office has on-site high-field MRI and X-ray.
Treatment
Non-surgical treatment is appropriate for grade I and most grade II isolated PLC injuries. It involves brace immobilization for several weeks, progressive range of motion, and a targeted physical therapy program focused on quadriceps strengthening and hip stability.
Surgical treatment is indicated for grade III isolated PLC injuries in active patients, for PLC injuries combined with ACL or PCL tears (the most common indication), and for chronic PLC insufficiency with persistent instability. Dr. Chudik performs PLC reconstruction using tendon graft to restore the LCL and popliteofibular ligament anatomically. Concomitant ACL or PCL reconstruction is performed at the same operation.
Acute PLC repair (within two to three weeks of injury) produces better outcomes than delayed reconstruction in specific injury patterns and is preferred when the patient is medically ready for surgery.
Recovery and Outcomes
Recovery after PLC reconstruction typically includes six weeks of brace protection in extension, progressive range of motion starting immediately but with external rotation protected, strengthening over three to four months, and return to sport at six to nine months. When combined with ACL or PCL reconstruction, recovery follows the longer multi-ligament timeline.
Outcomes after acute reconstruction of isolated PLC injury are good when all involved structures are anatomically addressed. Chronic PLC deficiency and missed PLC injury are leading causes of failed cruciate reconstruction, which is why its recognition and treatment matter.
When to See Dr. Chudik
Schedule an evaluation after any high-energy knee injury, after knee dislocation even if self-reduced, or if prior ACL or PCL reconstruction has not restored stability. Call 630-324-0402 or request an appointment online.