What is the posterolateral corner?
The posterolateral corner (PLC) of the knee is a complex of ligamentous and tendinous structures on the outer and back of the knee. The three primary stabilisers are the fibular collateral ligament (FCL), the popliteal tendon (PLT), and the popliteofibular ligament (PFL). Together they resist varus force, external rotation, and posterior translation of the tibia.
PLC injuries often occur alongside ACL or PCL tears, and it is the concomitant PLC injury that is commonly missed. If a cruciate ligament is reconstructed without addressing a concurrent PLC injury, the reconstruction will fail — which is one reason why thorough pre-operative assessment of the entire knee is essential.
How PLC injuries present
Patients typically describe instability on the outer side of the knee, particularly when pushing off on a straight leg or walking on uneven ground. On examination, a positive dial test (increased external rotation of the tibia compared to the other side) at 30° and 90° flexion is the key clinical finding. Varus stress testing confirms FCL involvement. MRI confirms the diagnosis and defines the extent of injury.
Signs suggesting PLC injury
- Lateral-side knee pain or giving way after high-energy trauma
- Positive dial test at 30° and 90°
- MRI showing FCL, popliteal tendon, or PFL signal change
- Associated ACL or PCL tear on imaging
Reconstruction vs repair — why reconstruction is preferred
For acute grade-III PLC injuries, primary repair (reattaching the torn structures) is sometimes performed if the tissues are of good quality and can be anatomically reduced. However, the evidence strongly favours reconstruction over repair.
What the evidence shows: Clinical outcomes data (JBJS Essential Surgical Techniques, Maheshwer et al., 2022) demonstrate that primary PLC repairs have significantly higher rates of reoperation and failure compared to reconstruction. Anatomic reconstruction of the three primary PLC stabilisers has shown improved subjective and objective outcomes compared to both non-surgical treatment and repair. Reconstruction is now the recommended approach for grade-III and chronic PLC injuries.
Surgery and recovery
Anatomic PLC reconstruction uses tendon grafts to reconstruct the FCL, popliteal tendon, and popliteofibular ligament in their native positions. It is a technically demanding procedure requiring careful anatomic knowledge to avoid peroneal nerve injury. When performed alongside cruciate reconstruction, staging may be considered.
Recovery involves protected weight-bearing for 6 weeks, followed by progressive rehabilitation. Return to sport is typically at 9–12 months. Full knee stability, assessed by objective testing, is the goal before returning to cutting or contact activities.
PLC injuries are rarely isolated — most occur alongside ACL or PCL tears. See the article on ACL and PCL reconstruction for more on multi-ligament knee injuries.
References (PubMed)
Maheshwer B, et al. Posterolateral Corner Reconstruction: Surgical Technique and Postoperative Rehabilitation. JBJS Essent Surg Tech. 2022;12(1). DOI: 10.2106/JBJS.ST.20.00047