The posterolateral corner is stabilised by static and dynamic structures and used to be called the ‘dark side’ of the knee due to its poorly understood anatomy. PLC injuries commonly are associated with PCL or ACL injuries and are seldom isolated. A missed PLC injury can be a cause of failure of ACL or PCL reconstructions. Acute PLC injuries are best repaired early (1-2 weeks) and chronic PLC injuries are ideally reconstructed using an anatomical technique.
What is a posterolateral corner injury?
The anatomy of the posterolateral corner is complex. In early evolution, the fibula articulated with the femur and the popliteus was attached to the tip of fibula. The fibula has since migrated distally and the popliteus attachment has moved to the femur.
MRI scans of acutely injured knees often show some oedema in the posterolateral corner with capsular injury associated with a pivoting injury. Not all of these posterolateral corner injuries would require repair.
Significant injury to the following structures causes instability to the posterolateral corner and would warrant acute posterolateral corner repair –
- Lateral collateral ligament
- Popliteo-fibular ligament
- In more severe PLC injury, there can be damage to IT band, Biceps femoris, lateral capsule and common peroneal nerve
Mechanism of Injury
PLC injuries occur with athletic trauma, motor-vehicle accidents and falls. Contact and non contact injuries can happen with hyperextension, varus load and tibial external rotation. Isolated PLC constitutes less than 5% of all plc injuries.
Leg alignment and Varus thrust in gait
VIDEO GOES HERE
The following video shows varus alignment and varus thrust. In the presence of a varus thrust, performing an isolated ACL or PCL reconstruction can lead to failure of reconstruction. An upper tibial osteotomy or a combined ligament reconstruction may be indicated.
External Rotation Recurvatum (Hughston)
Varus Stress Test
The lateral collateral ligament is palpable easily when the knee is placed in a figure of 4 position. The extent of joint opening can be measured on a stress xray.
The dial test may be a valuable diagnostic method in cases of injury to 3 posterolateral structures or combined injuries to the PCL and 2 posterolateral structures. However, posterolateral instability with injuries to only 1 or 2 posterolateral structures may not be clinically detected by the dial test.
Grading PLC injuries
PLC inuries produce varus and rotational instability. Houghston graded the injuries based on varus instability alone. To include the rotational instability with varus instability, Fanelli and Larsen provided a new classification.
- Type A – isolated rotational injury to the PFL and popliteus tendon complex.
- Type B – rotational injury with a mild varus component representing injury to PFL and popliteus tendon complex as well as attenuation of the LCL.
- Type C – significant rotational and varus component secondary to complete disruption of the PFL, popliteus tendon complex, LCL, lateral capsule, and cruciate ligament or ligaments.
Arthroscopy – The Drive Through Sign
Arthroscopy is useful to assess the posterior horn of the lateral meniscus, injuries to the coronary ligament, avulsions of the popliteus tendon off the femur, tears of the lateral capsular ligament and popliteomeniscal fascicles, and in assessing whether the major component of the posterolateral knee injury was meniscofemoral or meniscotibial based.
The “drive through sign” is exceptional posterior visualisation of the lateral meniscus with >1 cm of lateral compartment opening.
Management of Posterolateral Corner Injuries
Acute postero-lateral corner injury
- Grade 1/Grade 2 injuries- knee brace
- Grade 3- Acute Repair
- Severe Grade 3- Acute Reconstruction
Chronic PLC Injury
Grade 1 to 2 injuries (<10mm opening on varus stress with <10 degrees difference in external rotation on dial test)
The recommended treatment for patients with Grade 1 to 2 posterolateral knee complex injuries (partial injuries) initially is nonoperative. The knees are treated in a ROM brace that is kept locked for the first 3 weeks at 15 degrees. Static quadriceps exercises and Straight leg raises are commenced early. Patients are nonweightbearing for this initial period. At 3 weeks, patients are allowed to work on range of motion (ROM) to 90 degrees and commence weightbearing. It is important to start Closed chained quadriceps exercises, with the avoidance of active hamstring exercises for the first 6 to 10 weeks after injury.
Patients who complain of pain or instability at 3 months post injury need to be reevaluated carefully to determine whether they have any instability present in their knee or whether they have any varus thrust in gait. MRI scans are unhelpful in such situations. If the pain is accentuated by the examiner placing the knee in a figure-four position (the figure-of-four test), these patients may have a tear of their popliteomeniscal fascicles. Tearing of these fascicles results in increased lateral meniscal hypermobility and the meniscus is entrapped in the joint when the knee is put in the figure-four position. Patients may benefit from repair of the lateral meniscus back to the popliteomeniscal fascicles of the popliteal hiatus.
Grade 3 injuries (>10mm joint opening and/or >10 degrees external rotation on dial test)
Acute repair is generally better and nonoperative treatment is not recommended for grade 3 injuries. The timing of repair is critical and is ideally performed within 2 weeks. Delays beyond this period can make identification of posterolateral structures and soft tissue planes difficult.
In the presence of combined ligament injuries, PLC is repaired and ACL/PCL treated by simultaneous or delayed reconstruction. It is important to avoid arthrofibrosis.
Technique of Repair
- Check common peroneal nerve prior to surgery
- MRI scans useful to assess structures involved. Check biceps femoris as it is an important landmark for dissection.
- Dry arthroscopy useful as mentioned above
- Lateral curvilinear incision
- Identify Common Peroneal nerve through surgical window posterior to IT Band
- Fibular neck avulsion fracture fixed with anchors, screw with washer or tension band wiring.
- Inferior lateral geniculate artery may be encountered
- Femoral attachment of LCL and Popliteus identified through anterior window to Iliotibial Band and reattached anatomically using anchors, suture or recess technique.
- LCL attachtment on the femur is proximal and posterior to lateral epicondyle. The popliteus attachment is about 18mm anterior and distal to this point.
- Popliteo-fibular ligament is present in most patients and identified close to musculo-tendinous junction and repaired.
- Direct repair of midlateral capsule, IT band tear, meniscus tear or Biceps Femoris tear may be needed.
- Occasionally, augmentation with Hamstring graft or a slip of IT band or Biceps femoris may be necessary.
- Tensioning is done at 30 degress knee flexion and slight internal rotation and valgus.
Chronic injury to the posterolateral corner is a more difficult problem. The important aspects of injury assessment are alignment, gait and assessing coexisting ACL/PCL injury. Long leg alignment radiographs are essential and MRI scans are less helpful. Combined reconstruction has the best option of successful results.
If there is varus alignment, then a medial opening wedge tibial osteotomy is recommended. This contols varus laxity and external rotation even without repair/reconstruction of posterolateral structures (Arthur, LaPrade).
Reconstruction of the posterolateral corner has evolved from proximal advancement of posterolateral structures (Noyes, Hughston), nonanatomical reconstruction purely addressing LCL (Hughston, Clancy) to more anatomical reconstruction addressing popliteus and LCL (Larsen, LaPrade, Veltri and Warren, Noyes, Sekiya, Yoon). The anatomical reconstructions can be fibula based or Tibia and Fibula based with one or two femoral tunnels.
Techniques of Reconstruction
- Aim to regain range of motion
- Knee brace for 12 weeks
- Avoid active Hamstring exercises and external rotation of tibia for 3 months.
- Initial period of nonweightbearing followed by closed chain quadriceps physiotherapy and gentle leg presses from 6 weeks to 3 months.
- Exercise bike at 6 weeks with mini squats and proprioceptive exercises
- Treadmill and straight line activities at 4 months
- Sports after 10-12 months.
Outcomes of PLC Reconstruction
This link gives the evidence behind anatomical posterolateral corner reconstruction.
There are no prospective randomised studies comparing reconstruction techniques. Nau compared two different reconstruction techniques and found no significant difference in varus laxity. There can be a tendency to increased internal rotation.
Noyes(2007)- 14 knees, 2-13.7 years follow up- 13/14 knees had near normal varus laxity
Yoon (2006) compared anatomical reconstruction in 21 knees with a sling procedure in 25 knees. There was >5mm varus laxity in 14% of anatomical reconstructed knees.
Acute repair of PLC provides good results (Hughston, Krukhaug, Veltri) and is recommended over chronic reconstruction. Stannard compared repair and reconstruction and suggests that results from Acute repair is inferior to anatomical reconstruction.
Management of Common Peroneal nerve injuries with PLC injuries
Common Peroneal injuries are present in upto 41% of PLC with bicruciate injuries (Niall and Keating). Keating showed that complete recovery occurred in 21% and no useful recovery of motor or sensory function in 50%. There is also risk of nerve damage with surgical repair/reconstruction.
The management of the nerve injury and the rehabilitation of the ligament injury also becomes more complex.
Garozzo recommends surgical management of the nerve injury and that a transfer procedure to nerve repair enhances neural regeneration, dramatically improving the surgical outcome of these injuries.
Raheem O, Philpott J, Ryan W, O’Brien M. Anatomical variations in the anatomy of the posterolateral corner of the knee. Knee Surg Sports Traumatol Arthrosc. 2007 Jul;15(7):895-900. Epub 2007 Feb 15
Alpert JM, McCarty LP, Bach BR Jr. The posterolateral corner of the knee: anatomic dissection and surgical approach.J Knee Surg. 2008 Jan;21(1):50-4.
Veltri DM, Deng XH, Torzilli PA, Maynard MJ, Warren, RF. The role of the popliteofibular ligament in stability of the human knee. A biomechanical study. Am J Sports Med. 1996;24:19-27.
LaPrade RF, Resig S, Wentorf F, Lewis JL. The effects of grade III posterolateral knee complex injuries on anterior cruciate ligament graft force. A biomechanical analysis. Am J Sports Med. 1999;27:469-75.
Seebacher JR, Inglis AE et al. ‘The structure of the posterolateral aspect of the knee’. J Bone Joint Surg Am. 1982;64:536-541.
Hughston JC, Norwood LA Jr. The posterolateral drawer test and external rotational recurvatum test for posterolateral instability of the knee. Clin Orthop. 1980;147:82-7.
Covey DC. Current Concepts review. Injuries to the posterolateral corner of the knee. J Bone Joint Surg Am. 2001.83:106
LaPrade RF. Arthroscopic evaluation of the lateral compartment of knees with grade 3 posterolateral knee complex injuries. Am J Sports Med. 1997;25:596-602.
Bae JH, Choi IC, Suh SW, Lim HC, Bae TS, Nha KW, Wang JH.Evaluation of the reliability of the dial test for posterolateral rotatory instability: a cadaveric study using an isotonic rotation machine. Arthroscopy. 2008 May;24(5):593-8. Epub 2008 Jan 25
Noyes FR, Barber-Westin SD: Posterolateral knee reconstruction with an anatomical bone-patellar tendonbone reconstruction of the fibular collateral ligament. Am J Sports Med 2007;35:259-273.
Ricchetti ET, Sennett BJ, Huffman GR.Acute and chronic management of posterolateral corner injuries of the knee. Orthopedics. 2008 May;31(5):479-88; quiz 489-90
Krukhaug Y, Molster A, Rodt A, Strand T: Lateral ligament injuries of the knee. Knee Surg Sports Traumatol Arthrosc 1998;6:21-25.
Veltri DM, Warren RF. Isolated and combined posterior cruciate ligament injuries. J Am Acad Orthop Surg. 1993;1:67-75.
VeltriDM, WarrenRF: Operative treatment of posterolateral instability of the knee. Clin Sports Med 1994; 13:615-627
Albright JP, Brown AW. Management of chronic posterolateral rotatory instability of the knee: surgical technique for the posterolateral corner sling procedure. Instr Course Lect. 1998;47:369-78
Clancy WG Jr, Shepard MF, Cain EL Jr. Posterior lateral corner reconstruction. Am J Orthop. 2003;32:171-176
Fanelli GC, Feldmann DD. ‘Management of combined ACL/PCL/posterolateral complex injuries of the knee’. Oper Tech Sports Med. 1999;7:143-149.
StannardJP, BrownSL, FarrisRC, McGwinGJr, VolgasDA: The posterolateral corner of the knee: Repair versus reconstruction. Am J Sports Med 2005; 33:881-888.
FanelliGC, LarsonRV: Practical management of posterolateral instability of the knee. Arthroscopy 2002; 18(2 suppl 1):1-8
LarsonRV: Isometry of the lateral collateral and popliteofibular ligaments and techniques for reconstruction using a free semitendinosus tendon graft. Oper Tech Sports Med 2001; 9:84-90
Nau T, Chevalier Y, Hagemeister N, Deguise JA, Duval N. Comparison of 2 surgical techniques of posterolateral corner reconstruction of the knee. Am J Sports Med. 2005 Dec;33(12):1838-45
Laprade RF, Engebretsen L, Johansen S, Wentorf FA, Kurtenbach C. The effect of a proximal tibial medial opening wedge osteotomy on posterolateral knee instability: a biomechanical study. Am J Sports Med. 2008 May;36(5):956-60.
Arthur A, LaPrade RF, Agel J.Proximal tibial opening wedge osteotomy as the initial treatment for chronic posterolateral corner deficiency in the varus knee: a prospective clinical study. Am J Sports Med. 2007 Nov;35(11):1844-50.
Niall DM, Nutton RW, Keating JF. Palsy of the common peroneal nerve after traumatic dislocation of the knee. J Bone Joint Surg Br. 2005 May;87(5):664-7.
Garozzo D, Ferraresi S, Buffatti P. Surgical treatment of common peroneal nerve injuries: indications and results. A series of 62 cases. J Neurosurg Sci. 2004 Sep;48(3):105-12