The posterolateral corner of the knee is a complex of structures including the lateral collateral ligament, popliteus tendon, popliteofibular ligament, posterolateral capsule, and arcuate ligament that together resist varus forces and external tibial rotation. PLC injuries frequently accompany ACL and PCL tears in high-energy knee trauma, and failure to diagnose and repair the PLC is the most common cause of ACL and PCL graft failure.
| Origin | Fibular head, lateral tibial condyle, and lateral femoral condyle |
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| Insertion | Multiple attachments forming the posterolateral corner complex |
| Actions | Resists varus stress, external tibial rotation, and posterior tibial translation; the lateral equivalent of the posteromedial corner |
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The dial test (external tibial rotation test at 30 and 90 degrees) is the key physical examination manoeuvre for PLC injuries, with increased external rotation at 30 degrees implicating the PLC and additional increase at 90 degrees suggesting concurrent PCL injury. Isolated PLC injuries can be repaired primarily within 2 to 3 weeks, but chronic PLC deficiency requires reconstruction using graft tissue.
Combined LCL, popliteus tendon, and popliteofibular ligament disruption from varus contact force producing posterolateral instability confirmed by the dial test, requiring primary repair or reconstruction to prevent recurrent instability.
