The posterolateral corner of the knee comprises the LCL, popliteus tendon, popliteofibular ligament, arcuate ligament, and posterolateral joint capsule. Combined injury to these structures produces posterolateral rotatory instability — the positive dial test and external rotation recurvatum sign. PLC injuries are frequently missed in multiligament knee injuries and untreated PLC instability causes ACL and PCL reconstructions to fail.
| Origin | Lateral femoral condyle and fibular head |
|---|---|
| Insertion | Fibular head, proximal fibula, and lateral tibial condyle |
| Actions | Combined resistance to varus stress, external tibial rotation, and posterior translation — the posterolateral stabilising system |
|---|
The dial test (external tibial rotation at 30 degrees and 90 degrees of flexion compared bilaterally) identifies PLC injury when there is greater than 10 degrees external rotation asymmetry at 30 degrees but not 90 degrees. PLC reconstruction using figure-of-four technique or fibular-based anatomical repair is performed acutely (within 3 weeks) or with delayed staged reconstruction. Isolated ACL reconstruction with an unrecognised PLC injury has a very high failure rate.
Combined LCL, popliteus, and PLC capsular disruption producing external rotation instability confirmed by dial test, requiring anatomical reconstruction within 3 weeks.
