The posterolateral corner of the knee. Anatomy, biomechanics and management of injuries

The structures within the posterolateral corner of the knee have recently been "re-discovered" providing a very important role in maintaining the stability of the knee. Injury to the posterolateral corner is not common but neither is it rare; it is usually damaged in combination with rupture of one of the cruciate ligaments in direct and indirect trauma to the knee. When reconstructing a knee to restore stability following such injuries, it is important to recognise damage to the posterolateral corner so that this can be corrected. Ignored damage to this region may result in continuing knee instability and resultant failure of cruciate ligament reconstruction. We present a review of the anatomy and biomechanics of the structures in the posterolateral corner. This is then related to the diagnosis of injuries to the region via history, examination and imaging. We then discuss the management of injuries to the posterolateral corner describing our preferred method of repair.     

Anatomic Posterolateral Corner Knee Reconstruction

Injuries to the lateral collateral ligament and posterolateral corner of the knee, particularly when combined with anterior cruciate or posterior cruciate ligament injuries, can result in profound symptomatic knee instability. Although many surgical improvements have been made in reconstruction of anterior and posterior cruciate ligament injuries, reconstruction of the posterolateral corner has had less predictable results, with residual pathologic laxity especially in the chronic situation. This has stimulated many surgeons to recommend acute repair of posterolateral knee injuries. This article describes a more anatomic reconstruction of the posterolateral corner for chronic instability, recreating the lateral collateral ligament and popliteofibular ligament using either autogenous or allograft soft tissue and an interference screw technique. In a small clinical series, this has proven to restore varus rotation and external rotation patholaxities with a high degree of predictability.     

Injuries of the posterolateral corner of the knee

The complex anatomy of the posterolateral corner of the knee is due largely to the evolutionary changes in the anatomic relationships of the fibular head, the popliteus tendon, and the biceps femoris muscle. Recent research has improved our understanding of the popliteus complex, particularly the role of the popliteofibular ligament. Biomechanical studies provide a scientific basis for clinical examination of the knee with suspected injury of the posterolateral corner. All grade-I and most moderate grade-II injuries of the posterolateral structures can be treated nonoperatively, but residual laxity may remain, especially in knees with grade-II injury. Acute grade-III isolated or combined injury of the posterolateral corner is best treated early, by direct repair, if possible, or else by augmentation or reconstruction of all injured ligaments. Chronic injury of the posterolateral corner, whether isolated or combined, is probably best treated by reconstruction of the posterolateral corner along with reconstruction of any coexisting cruciate ligament injury. Failure to diagnose and treat an injury of the posterolateral corner in a patient who has a known tear of the anterior or posterior cruciate ligament can result in failure of the reconstructed cruciate ligament.     

Editorial Commentary: Those Who Don't Know History Are Condemned to Repeat It—What Are the Next Steps to Improve Posterolateral Knee Outcomes?

Two decades ago, it was not uncommon to call the posterolateral corner of the knee the “dark side of the knee.” This was because there were few quantitative anatomic data, no anatomic-based reconstructions, and a high rate of clinical outcome failures. Most nonanatomic posterolateral reconstruction procedures at the time commonly resulted in significant recurrent increases in varus gapping and significant overconstraint in external rotation. Postoperative protocols for treating these injuries were designed to often either cast or immobilize the operative knee for 2 to 6 weeks, which resulted in a higher incidence of arthrofibrosis. In addition, missed or neglected posterolateral corner injuries were frequently the cause of failed anterior and posterior cruciate ligament reconstruction graft failures. Anatomic-based posterolateral corner reconstructions have now been validated clinically to significantly improve patient outcomes. The next steps in improving patient outcomes would be to further refine these anatomic-based techniques, improve postoperative rehabilitation protocols, and ensure that future outcome studies have both patient-reported outcomes and objective data with stress radiographs to confirm that we are building a better mousetrap to treat this pathology.     

The posterolateral corner of the knee: anatomic dissection and surgical approach

The surgical anatomy and biomechanical role of the posterolateral corner of the knee has received significant attention in recent years. Nevertheless, because of the relative infrequency with which injuries to this area are treated operatively, the surgical approach to this area of the knee may be unfamiliar to many residents and practicing orthopedic surgeons. Accurate knowledge of the appropriate anatomy, planes of dissection, and surgical approach is vital to the safe access of these structures for purposes of repair or reconstruction. This article describes the step-by-step anatomic approach to the posterolateral corner of the knee using paired cadaveric images, with emphasis on the relevant surgical anatomy.     

An anatomic study of the popliteofibular ligament

Our study was prompted by the varied reports in literature about the existence of the popliteofibular ligament as an integral part of the posterolateral corner of the knee. We performed 25 formalinised cadaveric knee dissections and identified the popliteofibular ligament. It was on an average 11.06 (5-16) mm in width and 11.8 (6-16) mm in length. Our study did not include a functional evaluation. We found the ligament to be a constant structure of the posterolateral knee complex, and recommend its repair in acute injuries as well as reconstruction in chronic injuries of the posterolateral corner of the knee.     

Diagnosis and treatment of posterolateral knee injuries

Posterolateral knee injuries can be very debilitating. It is important to understand the complex anatomy and pertinent diagnostic tests to properly treat posterolateral knee injuries. The fibular collateral ligament, popliteus tendon, and the popliteofibular ligament are the main static stabilizers against abnormal varus and posterolateral translational moments. Important radiographic imaging studies for the posterolateral knee include full length anteroposterior radiographs, taken with the patient standing, to assess for varus alignment in patients with chronic injuries and high field (1.5 tesla or higher) magnetic resonance imaging with specific posterolateral knee sectioning. A physical examination that includes the external rotation recurvation test, varus stress test at 30 degrees, dial test at 30 degrees and 90 degrees, posterolateral drawer test, reverse pivot shift, and an assessment for a varus thrust gait are essential to properly diagnose a posterolateral knee injury. Patients with acute (< 3 weeks) anatomic repairs of Grade III posterolateral knee injuries have the best functional outcome. Although various surgical reconstruction techniques have been developed to treat chronic or irreparable acute posterolateral knee injuries, these techniques have not achieved outcomes comparable with the treatment of other ligament injuries of the knee. Techniques for anatomic reconstructions of these structures are just being developed. Improved education of clinicians as to the proper diagnosis of posterolateral knee injuries is necessary because a large number of these injuries still are missed on initial examinations. In addition, additional research into the most optimal posterolateral knee reconstruction techniques and outcome studies are needed to improve the treatment of this debilitating knee injury.     

Treatment of acute and chronic injuries to the posterolateral and lateral knee

Posterolateral instability of the knee is a complex problem in terms of diagnosis and treatment. Isolated injury to the posterolateral corner is uncommon and is usually associated with an injury to the anterior or posterior cruciate ligaments. It is difficult to isolate the effect of a posterolateral injury on instability of the knee when these combined instability patterns are present. Accurate diagnosis of posterolateral instability depends on the clinical history, a thorough knowledge of the anatomy of the posterolateral corner, and a complete knee examination. Because the instability is easily missed in the acute stage of the injury, chronic posterolateral instability develops. In the setting of combined ligamentous injury, all components of instability should be surgically addressed to achieve the best opportunity for success. In our experience, early diagnosis and reconstruction of posterolateral knee injuries are more successful than late reconstruction.     

Editorial Commentary: Prevention of Complications During Multiple Ligament Knee Injury Reconstruction: It’s Complicated!

Treatment of multiple-ligament knee injuries is complex and complicated. Surgeons should strive to keep their operative times under 5 hours, limit inside-out meniscal repair, consider fibular-based only posterolateral corner reconstructions (except in cases with associated proximal tibia-fibular joint injuries or massive posterolateral corner injuries), avoid acute surgery when possible, and proceed cautiously with ultra-low-velocity dislocations. Multiple-ligament knee injury reconstruction is challenging and complicated but a sincere thank you is extended to those surgeons who take on complex knee surgery.     

Posterolateral corner injury of the knee: evaluation and management

Posterolateral corner injury, an increasingly recognized entity, is commonly associated with concomitant ligament disruptions. Prompt recognition is critical for several reasons. Missed posterolateral corner injuries increase the failure rates for both anterior and posterior cruciate ligament reconstructions. Also, untreated posterolateral corner injuries lead to chronic disability. Acute (ie, immediate) surgical intervention results in superior outcomes compared with chronic (ie, late) reconstruction. Although no universal classification system has been adopted, attention to both varus and rotational stability is critical. Multiple options exist for posterolateral corner reconstruction, although recent trends have shifted toward anatomic reconstruction techniques.     

Posterolateral corner injuries of the knee: a serious injury commonly missed

We retrospectively reviewed the hospital records of 68 patients who had been referred with an injury to the posterolateral corner of the knee to a specialist knee surgeon between 2005 and 2009. These injuries were diagnosed based on a combination of clinical testing and imaging and arthroscopy when available. In all, 51 patients (75%) presented within 24 hours of their injury with a mean presentation at eight days (0 to 20) after the injury. A total of 63 patients (93%) had instability of the knee at presentation. There was a mean delay to the diagnosis of injury to the posterolateral corner of 30 months (0 to 420) from the time of injury. In all, the injuries in 49 patients (72%) were not identified at the time of the initial presentation, with the injury to the posterolateral corner only recognised in those patients who had severe multiple ligamentous injuries. The correct diagnosis, including injury to the posterolateral corner, had only been made in 34 patients (50%) at time of referral to a specialist knee clinic. MRI correctly identified 14 of 15 injuries when performed acutely (within 12 weeks of injury), but this was the case in only four of 15 patients in whom it was performed more than 12 weeks after the injury. Our study highlights a need for greater diligence in the examination and investigation of acute ligamentous injuries at the knee with symptoms of instability, in order to avoid failure to identify the true extent of the injury at the time when anatomical repair is most straightforward.     

The management of injuries to the medial side of the knee

Injuries to the medial side of the knee are the most common knee ligament injuries. The majority of injuries occur in young athletes during sporting events, with the usual mechanism involving a valgus contact, tibial external rotation, or a combined valgus and external rotation force delivered to the knee. Although most complete grade III medial knee injuries heal, some do not, which can lead to continued instability. For these patients, a thorough understanding of the presenting history and a physical examination are important because these injuries can often be confused with posterolateral corner injuries. The main anatomic structures of the medial side of the knee are the superficial medial collateral ligament, deep medial collateral ligament, and posterior oblique ligament. In addition, accurately locating 3 bony prominences over the medial aspect of the knee-the adductor tubercle, gastrocnemius tubercle, and medial epicondyle-is important to conduct a proper physical examination and for surgical repairs and reconstructions. Clinical diagnosis of medial knee injuries is primarily performed via the application of a valgus stress in full extension and at 30° of knee flexion. In addition, an examination of the amount of anteromedial tibial rotation is performed at 90° of flexion, while the dial test, performed at 30° and 90° of flexion, is important because it evaluates for rotational abnormalities. Valgus stress radiographs are useful to objectively determine the amount of medial compartment gapping and to discern whether there is medial or lateral compartment gapping when a medial or posterolateral corner knee injury cannot be differentiated, especially with a chronic injury. The majority of acute grade III medial knee injuries will heal after a nonoperative rehabilitation program. In most instances when there is a knee dislocation or multiligament injury, a primary repair with sutures may be indicated. In severe midsubstance injuries or chronic medial knee injuries, an anatomic medial knee reconstruction with grafts may be indicated. Rehabilitation principles for acute medial knee injuries involve controlling edema, regaining range of motion, and avoiding any significant stress on the healing ligaments. A well-guided rehabilitation program can result in excellent functional outcomes in the majority of patients.     

全关节镜下膝关节后外复合体重建

目的 介绍全关节镜下腘肌腱重建、腘肌腱联合腘腓韧带重建或膝关节后外复合体(posterolateral corner,PLC)解剖重建的手术技术,探讨全关节镜下PLC重建治疗膝关节后外不稳定的效果.方法 2008年8月至2010年4月,共完成全关节镜下后十字韧带(posterior cruciate ligament,PCL)+PLC重建手术34例.患者在接受手术时平均年龄34.1岁(15～52岁);男32例,女2例;从受伤到手术平均10.7个月.所有病例均为陈旧性损伤,且均为复合韧带损伤.所有PCL损伤的病例都存在PLC损伤.合并前十字韧带损伤6例(17.6%),合并前十字韧带、内侧副韧带损伤2例(5.9%),合并内侧副韧带损伤5例(14.7%).对膝关节PLC损伤进行分型,采用不同的重建技术进行治疗.对于A型旋转不稳定,采用全关节镜下腘肌腱重建、腘肌腱联合腘腓韧带重建;对于C型后外不稳定,采用全关节镜下PLC解剖重建.结果 14例患者获得随访并进行二次关节镜检查,平均随访18.5个月(13～25个月).终末随访包括:膝关节查体、KT-1000测量、膝关节应力像和胫骨外旋稳定性.使用膝关节应力像测量胫骨后移程度,胫骨后移由术前平均15.56mm减少为术后5.16mm,手术前后差异有统计学意义.使用屈膝30°位胫骨外旋试验评估膝关节后外旋转不稳定.对比患侧与健侧胫骨外旋的差值,由术前平均14.92°减小为术后-0.22°,手术前后差异有统计学意义.术后患者平均屈曲受限4.23°,无伸膝受限.结论 对于膝关节PLC损伤导致的不稳定,采用全关节镜下PLC重建的手术技术,能够有效恢复膝关节后外旋转不稳定.这种手术技术能够与PCL重建联合应用.

Abstract：

Objectiye To introduce the surgical technique of arthroscopy assisted anatomical posterolateral corner (PLC) reconstruction,including popliteal ligament,popliteofibular ligament and lateral collateral ligament,and evaluate the results of this technique.Methods From August 2008 to April 2010,34arthroscopic posterior cruciate ligament (PCL) and PLC reconstruction surgeries were performed.The average age of the patients was 34.1 (15-52) years.There were 32 males and 2 females.The average time period from injury to surgery was 10.7 months.All patients were chronic injuries and combined ligament injuries,including PCL and PLC injuries.Some cases had other ligament injury,including 6 patients of anterior cruciate ligament (ACL) injury (17.6%),2 of ACL combined medial cruciate ligament (MCL) injuries (5.9%),and 5 of MCL injuries (14.7%).According to Fanellis classification,for type A posterolateral rotation instability,we performed arthroscopic popliteal ligament reconstruction or popliteal ligament combined popliteofibular ligament reconstruction.For type C posterolateral instability,we performed arthroscopic PLC anatomical reconstruction.Results During the follow-up period,14 patients had undergone a second look arthroscopic examination and removal of hardware.The average follow-up time was 18.5 months (13-25 months).At the final follow-up,physical examination,stability evaluation with KT-1000 and Telos stress view,and dial test were performed.The posterior displacement of the knee had decreased from 15.56 mm preoperatively to 5.16mm postoperatively.The external rotation instability had decreased from 14.92° preoperatively to -0.22°postoperatively.The average limitation of knee flexion was 4.23° and no knee extension was limited.Conclusion With the surgical technique of arthroscopy assisted anatomical PLC reconstruction,we can restore the external rotation stability of knee.This technique can be performed combine with PCL reconstruction.     

Editorial Commentary: Small Incisions Can Make Big Mistakes: Knee Lateral Collateral Ligament Reconstruction Is All About the Anatomy!

It is becoming increasingly recognized that isolated lateral collateral ligament (LCL) tears are more common than have been previously recognized and that anatomic-based LCL reconstructions have the best outcomes. Although it was believed that posterolateral corner injuries were often missed or mistreated and were given the pneumonic of "the dark side of the knee," we are getting to the point where most of these more severe injuries are being recognized, and it is the isolated LCL injuries that are still less well recognized. Failure to treat LCL tears at the same time as a cruciate ligament reconstruction is a well-known cause of both anterior cruciate ligament and posterior cruciate ligament reconstruction graft failure. Therefore, either having the required clinical experience or knowledge, or using a radiographic backup method when one is not sure about the anatomic placement, is essential to correctly perform an LCL reconstruction.     

Acute and chronic posterolateral rotatory instability of the knee

Isolated posterolateral rotatory instability of the knee is an uncommon injury pattern that may result in significant degrees of functional disability. This injury complex can be a challenging diagnostic and therapeutic problem for the orthopaedic surgeon. The presence of associated ligamentous and soft-tissue injuries, resulting in combined instability patterns, further complicates management. The results of recent research have enhanced our understanding of the complex anatomy and biomechanics of the posterolateral aspect of the knee. Numerous surgical techniques have been described for both repair and reconstruction of the injured posterolateral structures; however, long-term functional results have been only moderately successful.     

Double-bundle PCL and Posterolateral Corner Reconstruction Components are Codominant

A more complete biomechanical understanding of a combined posterior cruciate ligament and posterolateral corner knee reconstruction may help surgeons develop uniformly accepted clinical surgical techniques that restore normal anatomy and protect the knee from premature arthritic changes. We identified the in situ force patterns of the individual components of a combined double-bundle posterior cruciate ligament and posterolateral corner knee reconstruction. We tested 10 human cadaveric knees using a robotic testing system by sequentially cutting and reconstructing the posterior cruciate ligament and posterolateral corner. The knees were subjected to a 134-N posterior tibial load and 5-Nm external tibial torque. The posterior cruciate ligament was reconstructed with a double-bundle technique. The posterolateral corner reconstruction included reattaching the popliteus tendon to its femoral origin and reconstructing the popliteofibular ligament. The in situ forces in the anterolateral bundle were greater in the posterolateral corner-deficient state than in the posterolateral corner-reconstructed state at 30° under the posterior tibial load and at 90° under the external tibial torque. We observed no differences in the in situ forces between the anterolateral and posteromedial bundles under any loading condition. The popliteus tendon and popliteofibular ligament had similar in situ forces at all flexion angles. The data suggest the two bundles protect each other by functioning in a load-sharing, codominant fashion, with no component dominating at any flexion angle. We believe the findings support reconstructing both posterior cruciate ligament bundles and both posterolateral corner components. One or more of the authors (CDH) have received funding from the Aircast Foundation, Pittsburgh, PA. Each author certifies that his or her institution either has waived or does not require approval for the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.     

Posterolateral reconstruction using split achilles tendon allograft

Injury to the cruciate ligaments of the knee commonly occurs in association with posterolateral instability, which can cause severe functional disability including varus, posterior translation, and external rotational instability. Failure to diagnose and treat an injury of the posterolateral corner in a patient who has a tear of the cruciate ligament can also result in the failure of the reconstructed cruciate ligament. Unlike isolated posterior cruciate ligament injury, there seems to be a consensus of opinion that injury to the posterolateral corner, whether isolated or combined, is best treated by reconstructing the posterolateral corner along with the coexisting cruciate ligament injury, if combined. Commonly proposed methods of reconstructing the posterolateral corner have focused on the reconstruction of the popliteus, the popliteofibular ligament, and the lateral collateral ligament. We introduce a new technique for reconstructing the posterolateral corner using a split Achilles tendon allograft. Our method reasonably addresses the several pitfalls in the reconstruction of the posterolateral corner, including (1) concurrent reconstruction of important posterolateral structures, (2) regaining the isometry of the lateral collateral ligament, (3) repositioning the reconstructed popliteus into its original position, and (4) providing a secure fixation method.     

Medial and lateral segond fractures in a skeletally immature patient: a radiographic marker for the multiply injured knee

Marginal fractures of the medial tibial plateau have been reported in the literature as a secondary type of Segond fracture. Some reports described this entity in the setting of combined injuries such as root avulsions of the medial meniscus, complete disruption of the posterior cruciate ligament (PCL), partial tear of the anterior cruciate ligament (ACL), and tears of the medial meniscus and medial collateral ligament. It has been postulated that medial marginal fractures are secondary to compression of the medial aspect of the femoral condyle and tibial plateau with a corresponding posterolateral corner injury. However, this mechanism of injury may not always be as straightforward.This article presents a case of an alternate injury pattern in a skeletally immature patient. A 16-year-old boy sustained a varus force and twisting injury to his knee, resulting in radiographic evidence of multiple avulsion fractures of the knee, including a fibular epiphyseal avulsion fracture and medial and lateral Segond fractures. Usually, the avulsion fractures serve as markers for significant ligamentous injuries in adult patients, but our patient had minimal injury to the PCL, ACL, and posterolateral corner. Further physical examination and imaging studies revealed an anterior horn root avulsion, meniscocapsular separation, and anterior cortical rim fracture. A combination of imaging modalities helped us further characterize the injury pattern to devise the optimal surgical plan, especially the fixation of the anterior cortical fracture of the tibia.     

Osteotomy about the knee: applications, techniques, and results

Varus or valgus malalignment of the knee may be either a cause or a consequence of unicompartmental knee arthritis in young, active adults. Proximal tibial osteotomy for the varus knee and distal femoral osteotomy for the valgus knee have been used for decades to manage this condition; however, their use has decreased significantly in recent years as the popularity of unicompartmental and total knee arthroplasty has grown. With the advent of biologic resurfacing techniques for focal full-thickness articular cartilage injury, combined or staged high tibial osteotomy is becoming increasingly popular. In addition, in the face of cruciate ligamentous instability with or without posterolateral corner instability coupled with varus malalignment, high tibial osteotomy with and without ligament reconstruction provides a solution to complex orthopedic problems. Recent long-term follow-up studies have concluded osteotomy allows for improved function and pain relief in properly selected young patients.