Special Tests for Posterolateral Corner Injuries

Introduction

The posterolateral corner is comprised of multiple ligament and tendon structures. The primary role of the posterolateral corner is to prevent external rotation of the tibia, provide varus stress, and resist posterior translation of the tibia (2). The primary stabilizers are the lateral collateral ligament (LCL), popliteus tendon, and popliteofibular ligament (4). The LCL is primarily responsible for provided varus stability (1). The popliteus tendon will also prevent varus translation, but also resist external rotation of the tibia (1). Similarly, the popliteofibular ligament will also prevent external rotation of the tibia and act as a secondary support to prevent varus stress and posterior tibia translation (1,3). Finally, the PCL will prevent posterior translation of the tibia (1).

Cadaver dissection of the posterolateral corner (6)

The distal and deep portion of the iliotibial band is also part of the posterolateral corner (2).  Also included in the posterolateral corner is the distal portion of the biceps femoris at the insertion of the fibula styloid (2). The head of the lateral gastrocnemius muscle is also considered a part of the posterolateral corner (2). The fabello-fibula ligament and arcuate ligament are also stabilizing structures found in the posterolateral corner (5).

Image of the structures of the posterolateral corner (7). Label A is the lateral gastrocnemius, B is the popliteofibular ligament, C is the popliteus muscle and liagment, D is the lateral collateral ligament (7). 

The structures of the posterolateral corner are susceptible to damage during multiligamentous knee injuries, but isolated injuries can exist as well (4). 

Diagnosis

Physical exam is the primary determinant of rotational stability of the knee (1). A standard knee exam needs to be done that includes inspection, palpation, assessment of the knee range of motion, leg strength, and then special tests. The evaluation should include assessment of the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and lateral collateral ligament. There are multiple special tests that help assist in diagnosis of a posterolateral corner injury.

The first test we will review is the varus stress test. With the patient in supine position, the knee should be evaluated in both 0 degrees of extension and 30 degrees of extension (4). Providers will add a varus stress to the knee and compare for laxity and pain from side to side (4).

 

Varus stress test at 0 and 30 degrees of knee flexion (6)

The next test to review is the Dial test. The Dial test is typically performed with the patient in prone position. The patient’s knees will be positioned in both 90 degrees and 30 degrees for the exam (1). The provider will apply an external rotation stress to both feet and compare the amount of external rotation from side to side (1). An increase in external rotation of 10-15 degrees with the knee flexed to 30 degrees may indicate a posterolateral corner injury (4). However, if the same degree of external rotation is seen with the knee flexed to 90 degrees, then a posterolateral corner and PCL injury are suspected (4).

 

Dial test evaluating at 90 and 30 degrees of knee flexion (4)

The third test to review is the external rotation recurvatum test. The patient will be placed in supine position (4). One hand will stabilize the distal thigh and one hand will be lifting the leg by the great toe (4). A positive test is seeing hyperextension of the joint compared to the contralateral side (4).

 

External rotation recurvatum test (1)

The final test to review is the reverse pivot shift test. The patient will be placed in supine position (4). The knee will first be placed in 90 degrees of flexion (1). Then the tibia is externally rotated and a valgus stress will be applied to the knee and maintaining this stress, the knee will be brought into extension (4).

Reverse pivot shift test (1)

MRIs are typically done to evaluate the posterolateral corner soft tissue structures. 

Conclusion

The posterolateral corner is a complex structure that consists of both primary and secondary stabilizers. The primary stabilizers are the lateral collateral ligament, popliteus tendon, and popliteofemoral ligament. The secondary stabilizers include the posterior collateral ligament, distal portion of the biceps femoris, IT band, and lateral gastrocnemius muscle. Special tests used to diagnose an injury in the posterolateral corner include a reverse pivot shift test, dial test, and external rotation recurvatum test.

By Gregory Rubin, DO
rubinsportsmed.com

References

1)      Swinford, Steven T., et al. “Biomechanics and Physical Examination of the Posteromedial and Posterolateral Knee: State of the Art.” Journal of ISAKOS, vol. 5, no. 6, Nov. 2020, pp. 378–88. ScienceDirect, https://doi.org/10.1136/jisakos-2018-000221.

2)      Porrino, Jack, et al. “An Update and Comprehensive Review of the Posterolateral Corner of the Knee.” Radiologic Clinics of North America, vol. 56, no. 6, Nov. 2018, pp. 935–51. PubMed, https://doi.org/10.1016/j.rcl.2018.06.006.

3)      Stannard, James P., et al. “The Posterolateral Corner of the Knee: Repair versus Reconstruction.” The American Journal of Sports Medicine, vol. 33, no. 6, June 2005, pp. 881–88. PubMed, https://doi.org/10.1177/0363546504271208.

4)      Maniar, Adit R., et al. “Posterolateral Corner of the Knee: An Update on Current Evaluation and Management Strategies.” The Journal of the American Academy of Orthopaedic Surgeons, vol. 32, no. 1, Jan. 2024, pp. e13–23. PubMed, https://doi.org/10.5435/JAAOS-D-23-00278.

5)      Nannaparaju, M., et al. “Posterolateral Corner Injuries: Epidemiology, Anatomy, Biomechanics and Diagnosis.” Injury, vol. 49, no. 6, June 2018, pp. 1024–31. PubMed, https://doi.org/10.1016/j.injury.2017.10.008.

6)      Chahla, Jorge, et al. “Posterolateral Corner of the Knee: Current Concepts.” The Archives of Bone and Joint Surgery, vol. 4, no. 2, Apr. 2016, pp. 97–103.

 

7)      Shon, Oog-Jin, et al. “Current Concepts of Posterolateral Corner Injuries of the Knee.” Knee Surgery & Related Research, vol. 29, no. 4, Dec. 2017, pp. 256–68. PubMed, https://doi.org/10.5792/ksrr.16.029.