Where is the posterolateral corner

Rezaee, A. Posterolateral corner injury of the knee. Reference article, Radiopaedia. Trauma , Musculoskeletal. URL of Article. On this page:. The Posterolateral Corner of the Knee.

Examination of Posterolateral Corner Injuries. J Knee Surg. Rosas H. Unraveling the Posterolateral Corner of the Knee. Journal of Osteopathic Medicine. Posterolateral Corner of the Knee: Current Concepts. These include the external rotation recurvatum test, varus stress test at 30 degrees, dial test at 30 and 90 degrees, posterolateral drawer test, reverse pivot shift, and a gait exam. In the external rotation recurvatum test, the patient lies supine and the leg is suspended by the toe.

The test is positive when the lower legs falls into external rotation and knee recurvatum and varus. In the varus stress test, the patient is supine, and the knee is flexed to 30 degrees. The examiner then introduces a varus force from the ankle, with their other hand monitoring the lateral joint line for increased opening.

Varus laxity at 30 degrees indicates an isolated LCL injury If there were to be varus laxity at 0 degrees of flexion, there is likely an LCL and cruciate injury In the dial test, the patient is supine, and the knee is flexed to 30 or 90 degrees.

The physician then externally rotates the ankle, creating an external rotation force at the knee. The relative external rotation of the tibial tubercle of the affected knee is qualitatively assessed in comparison to the non-affected knee.

This test has been criticized by some as being too subjective and is difficult to interpret In the posterolateral drawer test, the patient is supine, and the hip is flexed to 45 degrees, the knee is flexed to 90 degrees and the foot is externally rotated 15 degrees Then, a posterolateral force is then applied to the knee, and the amount of posterolateral rotation of the tibia on the femur is qualitatively measured compared with the unaffected knee In the reverse pivot shift test, the patient is supine, and the hip is flexed to 70 degrees, the knee is flexed to degrees and the foot is externally rotated This leads to a posterolateral subluxation of the tibia on the femur.

The knee is then slowly extended and is observed for a reduction of the tibia with a palpable clunk Lastly, a gait exam should also be performed.

Patients with a PLC injury will often demonstrate a varus knee thrust at the time of the foot strike in the gait cycle 2, Based on the above physical exam techniques, injuries are graded as minor, moderate or severe sprains based upon the Modified Hughston Criteria, summarized in the table below:. Figure 4: Modified Hughston Classification. Standard plain AP and lateral radiographs of the knee should be obtained in the setting of a suspected PLC injury Plain radiographs may show a Segond fracture—which is an avulsion of the meniscotibial portion of the mid third lateral capsular ligament and anterior arm of the short head of the biceps femoris off the proximal lateral tibia 15 , or an Arcuate fracture—which is an avulsion of the fibular styloid Bilateral varus stress radiographs are also be helpful in evaluating for PLC injury.

To generate this view—the patient is supine, and an angled foam block is inserted underneath the knee to obtain a standard 20 degrees of knee flexion. Then, the clinician applies a maximum varus force by placing one hand on the medial femoral condyle and one hand on the lateral aspect of the foot, and an image is taken. This is repeated on the non-injured leg, and the side to side difference SSD in lateral compartment gapping is calculated.

The popliteus tendon provides significant resistance to external tibial rotation, while the popliteofibular ligament provides both varus and external rotation stability.

Together these tissues also resist hyperextension over-straightening of the knee; therefore, any forceful movements into external tibial rotation, varus, hyperextension or combinations of these positions can injure the PLC structures. In the early stages following injury, the individual may complain of pain at the posterolateral aspect of the knee and the relevant soft tissues, or their points of insertion to bone, are usually tender on palpation poking.

Numerous PLC structures, including the LCL and popliteofibular ligament, attach to the head of the fibula and may avulse pull away bone during injury figure 3. Tenderness at the fibular head may indicate a knee fracture and X-ray is therefore required to confirm or exclude this diagnosis. Pain may also be present in the medial inside compartment due to impaction of the bones during the injury. The LCL is an extra-articular structure located outside the joint ; therefore, injury to this ligament can result in localised lateral knee swelling.

However, LCL injury rarely occurs without injury to an intra-articular structure located inside the knee joint , therefore PLC injury usually presents with swelling within the knee joint effusion.

PLRI occurs when there is excessive posterior translation and lateral rotation of the lateral tibial plateau and the individual may walk with their lower leg and foot internally rotated to avoid placing the knee in this unstable position. Unrecognised or untreated PLC injuries place greater strain on surgically reconstructed cruciate ligaments, which subsequently increases the risk of graft failure and further knee instability.

In long-standing chronic cases, posterolateral knee instability can place excessive loads on the medial compartment of the knee, which in turn can lead to degenerative changes and associated medial knee symptoms. The common peroneal nerve transmits signals from the skin to the central nervous system for sensation, and signals from the central nervous system to the muscles for muscular contraction. This nerve is affected in up to Individuals with weakness due to common peroneal nerve injury may walk with a foot drop gait.

As a priority, it is therefore important to assess for vascular injury in cases of known or suspected knee dislocations. Clinical tests that quantify adduction varus , posterolateral rotation of the tibia or hyperextension recurvatum of the knee have been recommended to assess the integrity of the PLC.

For details on the diagnostic accuracy of clinical tests for PLC injury, please visit the statistics section. This test is performed with the patient supine on their back or prone on their front and knees together. The amount of external tibial rotation is compared between sides at both angles, using the medial borders of the feet for reference video 3. As the knee flexes bends further, the PCL provides more resistance to external tibial rotation.

The foot and leg is externally rotated, an axial load is applied through the foot and a valgus force applied to the knee via the proximal fibula. This test is performed with the patient lying supine. The thigh is stabilised with one hand and the heel is lifted off the bed with the other hand by pulling upwards on the big toe video 5.

The extra movement at the knee is caused by a combination of anterior translation, varus angulation and external rotation of the tibia. A posterolateral force is then applied to the tibia, with a finger on the posterolateral aspect of the knee assessing for laxity video 6. The figure 4 test is performed with the patient supine or sitting, with the heel on the opposite leg, hip flexed, abducted and externally rotated; the leg will look like the number 4.

The LCL is palpated for side to side difference. The examiner applies a varus stress to both knees while simultaneously palpating the posterolateral structures for side-to-side difference in joint gapping and tissue integrity. This manoeuvre can be repeated at various knee angles as required video 7. A side-to-side difference in joint gapping or tissue integrity constitutes a positive test, which is considered diagnostic of posterolateral instability.

An increase in gapping on the injured side is graded as follows table 1 :. It is important to note that this scale is based on the perceived amount of gapping and the actual values, as measured with X-ray varus stress radiographs , are less than proposed.

Fanelli grading scale: this scale grades posterolateral instability by combining the findings of the external rotation and varus stress tests table 2.

If PLC injury is suspected, imaging can be ordered to assist diagnosis and to guide management. In long-standing presentations, a standing long leg X-ray figure 4 can identify leg malalignment that may require correction before, or during, PLC surgery.

A line drawn from the head of the femur to the ankle indicates the mechanical access of the leg. If the mechanical axis falls medial to the Fujisawa point, there will more stress on the PLC, which may increase the risk of failure following PLC surgery. Figure 4: standing long leg X-ray showing the mechanical axis white and blue lines and Fujisawa point. ACL, traumatic meniscal tears. Knee Review Article. Letter to the Editor.

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Translate this page into: English. The Posterolateral Corner: Explanations and Outcomes. Robert F. Floyd 2 , Gregory B. Abstract In this review, we examine the current understanding of posterolateral corner PLC injuries and treatment methods. Keywords Posterolateral corner Fibular collateral ligament Lateral collateral ligament Popliteofibular ligament Popliteus tendon Varus stress. Show Related Articles from PubMed. Figure Proximal and distal attachments of the fibular collateral ligament FCL and bony anatomy of the distal lateral femur.

The proximal attachment of the FCL can be seen attaching in a shallow depression 1. The popliteus tendon PLT attaches in the anterior fifth of the popliteus sulcus, The popliteofibular ligament can be seen in a , arising from the musculotendinous junction of the PLT and attaching to the downslope of the styloid process of the fibular head. The lateral meniscus can also be seen. Export to PPT. Table Surgical pearls and pitfalls. Pearls Pitfalls Perform posterolateral approach first to visualize the anatomy before fluid extravasation Scarring and an avulsed BF tendon can make the location of the common peroneal nerve unpredictable.

Go slow with the neurolysis Incise the biceps bursa in order to identify the FCL fibular attachment, 28 mm distal to fibular styloid and 8 mm posterior to anterior border of fibula Reaming the fibular head tunnel too proximally risks fracture or blowout Tag any remnant FCL to assist in identifying femoral FCL origin Validate that femoral PLT and FCL pins are Figure The posterolateral corner.

The three primary stabilizers of the posterolateral corner are the fibular collateral ligament FCL , the popliteus tendon, and the popliteofibular ligament. Also pictured are the lateral gastrocnemius tendon and the lateral meniscus. The long head of the biceps femoris tendon attaches on the lateral aspect of the fibular head.

Normally, the anterior arm would obscure the distal insertion of the FCL. In this image, the anterior arm has been removed to visualize the distal FCL. Normally, this distal attachment of the FCL is located in a bursa between the anterior and direct arms of the biceps femoris tendon. Figure Additional features of the posterolateral corner PLC. In Part a , the anterior A and posterior P divisions of the popliteofibular ligament are evident.

Part b shows the anterior arm of the biceps femoris tendon obscuring the insertion of the fibular collateral ligament on the lateral fibular head. The proximal tibialis anterior is also visible and makes plain the danger to anterior compartment musculature if the tibial tunnel is malpositioned during PLC reconstruction.

Figure The external rotation recurvatum test takes advantage of the increased heel height seen in patients with posterolateral corner PLC injuries. Historically used to grade PLC tear severity, the heel height test now is now understood to indicate the presence of a combined anterior cruciate ligament ACL and PLC injury. A side-to-side difference in heel height of 2. As the distal thigh is stabilized with one hand and the foot lifted by the great toe with the other, a knee with a combined PLC and ACL injury will demonstrate an increased heel height as the tibia undergoes anterior subluxation and slips into external rotation.

Figure Varus stress radiographs. Varus stress radiography is a validated tool for evaluating injuries of the posterolateral corner. A greater than 2. Attenuation of the fibular collateral ligament and avulsion of the popliteus tendon can be seen arrows. In b , a common radiographic sign of acute PLC injuries can be seen. Figure a and b Anatomic reconstruction of the posterolateral corner PLC. This image displays the final appearance of an anatomic PLC reconstruction procedure, which restores the native anatomy of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon.

The authors use a longitudinally split Achilles tendon allograft, with a fibular head and transtibial tunnel and interference screws for fixation.

This image first appeared in LaPrade et al. AJSM;32 6 The anatomic attachment of the FCL on the lateral femoral condyle is During anatomic posterolateral corner reconstruction, a guide pin is first placed through the femoral attachment of the popliteus tendon. After the correct distance is verified, a guide pin is placed for the FCL femoral tunnel.

When correct positioning of both pins is verified, a 9 mm reamer is then used to create FCL and PLT graft tunnels to a depth of 25 mm. A collateral ligament guide b is useful in overreaming the guide pins. Figure Intraoperative view of anatomic posterolateral corner PLC reconstruction. The FCL graft passes anterolaterally to posteromedially through the fibular head tunnel and, along with the PLT, is passed posterior to anterior through a tibial Tib tunnel. After fixation in the fibular head, the remainder of the FCL graft serves as a PFL graft and stabilizes the proximal tibiofibular joint.

Treatment or acute and chronic combined anterior cruciate ligament and posterolateral knee ligament injuries.