Vol 8, No 2, March/April 2000 97 Injuries involving the posterolateral structures of the knee are significantly less common than those affecting the medial or anterolateral structures, but may result in greater degrees of disability. The overall incidence of acute posterolateral rotatory instabil- ity (PLRI) has been reported to be less than 2% of all acute ligamentous knee injuries. 1 Because the complex anatomy and biomechanics of the posterolateral structures are not com- pletely understood, PLRI of the knee represents a challenging diagnostic and therapeutic problem for the orthopaedic surgeon. Historically, PLRI has been de- fined as the instability pattern that results from an injury to the arcuate ligament complex. It has been pos- tulated that the lateral tibial plateau externally rotates around the axis of the intact posterior cruciate liga- ment (PCL) and subluxates posteri- orly in relation to the lateral fe- moral condyle. 2 This concept of the PCL as the center of rotation of the knee has been challenged; it is now believed that a coupled relationship exists between the posterolateral structures and the cruciate liga- ments. As a result, a high incidence of combined injury patterns is observed clinically, including an- terolateral and anteromedial insta- bility in addition to PLRI. Hugh- ston et al 2 observed that 12 of 28 patients (43%) with chronic PLRI exhibited combined injury patterns. Baker et al 3 observed a similar trend in 10 (59%) of 17 patients, as did DeLee et al 1 in 22 (65%) of 34 patients and Hughston and Jacob- son 4 in 77 (80%) of 96 patients. Thus, concurrent ligamentous in- juries in other areas of the knee should be suspected in cases of acute and chronic PLRI. Anatomy There is a close structural relation- ship among the structures of the posterolateral corner of the knee. Some studies have suggested that it is impossible for an isolated popli- teus tendon injury to occur without associated weakening of other components of the posterolateral complex. 5 The overall functional and clinical significance of these interrelated structures is not yet completely understood. Hughston et al 2 defined the arcuate ligament complex as the functional tendi- nous and ligamentous complex consisting of the lateral collateral ligament (LCL), the arcuate liga- ment, the popliteus muscle and tendon, and the lateral head of the gastrocnemius. These constituents form a sling that functions stati- cally and dynamically to control rotation of the lateral tibiofemoral articulation. Dr. Chen is Chief Resident Physician, Department of Orthopaedic Surgery, Hospital for Joint Diseases, New York. Dr. Rokito is Assistant Director, Sports Medicine Service, Department of Orthopaedic Surgery, Hospital for Joint Diseases. Dr. Pitman is Director, Sports Medicine Service, Department of Orthopaedic Surgery, Hospital for Joint Diseases. Reprint requests: Dr. Chen, Department of Orthopaedic Surgery, Hospital for Joint Diseases, 301 East 17th Street, New York, NY 10003. Copyright 2000 by the American Academy of Orthopaedic Surgeons. Abstract Isolated posterolateral rotatory instability of the knee is an uncommon injury pattern that may result in significant degrees of functional disability. This in- jury 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 man- agement. 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 recon- struction of the injured posterolateral structures; however, long-term functional results have been only moderately successful. J Am Acad Orthop Surg 2000;8:97-110 Acute and Chronic Posterolateral Rotatory Instability of the Knee Frank S. Chen, MD, Andrew S. Rokito, MD, and Mark I. Pitman, MD Seebacher et al 6 developed a three- layer concept of the posterolateral structures (Fig. 1). Layer I, the most superficial layer, consists of the ilio- tibial band with its expansion ante- riorly and the superficial portion of the biceps femoris with its expansion posteriorly. The peroneal nerve lies deep and posterior to the biceps ten- don at the level of the distal femur. Layer II consists of the quadriceps retinaculum anteriorly and the pa- tellofemoral ligaments posteriorly. The most important and deepest layer, layer III, is composed of (1) the lateral joint capsule and coronary ligament, (2) the popliteus tendon, (3) the LCL, and (4) the fabellofibular and arcuate ligaments (Fig. 2). There is significant anatomic variability in the structures of this deepest layer. The arcuate and fabellofibular liga- ments are both present in approxi- mately 67% of patients. The fabello- fibular ligament is present alone in 20% of casesÑusually denoted by radiographic evidence of a large fa- bella. The arcuate ligament is pres- ent alone in the remaining 13% of the population, as suggested by the absence of the fabella or its cartilagi- nous remnant. 6 Iliotibial Band The iliotibial band, which runs between the supracondylar tubercle on the femur and GerdyÕs tubercle on the proximal tibia, is an impor- tant stabilizer of the lateral com- partment. The most important por- tion of this structure acts as an accessory anterolateral ligament. 7 During knee flexion, the iliotibial band becomes tight and moves pos- teriorly, exerting an external rota- tional and backward force on the lateral tibia. During knee exten- sion, it moves anteriorly and is thus spared in most cases of varus stress and posterolateral injury. Lateral Collateral Ligament The LCL originates proximally on the lateral femoral condyle and inserts on the fibular head, rein- forcing the posterior third of the capsule. The LCL is the primary static restraint to varus stress of the knee. 1,8 In addition, the LCL also provides resistance to external rota- tion. Biomechanical studies have shown that more than 750 N of force is required to cause failure of the LCL. 8 Isolated injuries to the LCL are uncommon and usually oc- cur in conjunction with injuries to other ligamentous and soft-tissue structures. Popliteus The obliquely oriented popli- teus, which originates from the posterior aspect of the tibia and passes through a hiatus in the coro- nary ligament to insert onto the lat- eral femoral condyle, reinforces the posterior third of the lateral cap- sule and forms the lower part of the floor of the popliteal fossa. 9 The popliteus also possesses at- tachments to the lateral meniscus in most of the population, poten- tially contributing to the dynamic stability of this structure. Electro- myographic studies have shown that the popliteus plays a major role in both dynamic and static sta- bilization of the lateral tibia on the femur, including restriction of pos- terior tibial translation, restriction of external and varus rotation of the tibia, and dynamic internal rotation of the tibia. Popliteofibular Ligament The popliteofibular ligament represents a direct static attachment of the popliteus tendon from the posterior aspect of the fibular head to the anterior aspect of the lateral femoral epicondyle. 9,10 It provides a significant share of the overall mechanical resistance to posterior tibial translation, external rotation, and varus rotation; a force of more than 400 N is required to cause fail- ure of this ligament. 8,10 In one study, 10 it was present in 10 of 11 Posterolateral Rotatory Instability of the Knee Journal of the American Academy of Orthopaedic Surgeons 98 Figure 1 Coronal section of the knee illustrates the three-layer concept of the anatomy of the posterolateral structures, as described by Seebacher et al. (Adapted with permission from Seebacher JR, Inglis AE, Marshall JL, Warren RF: The structure of the posterolateral aspect of the knee. J Bone Joint Surg Am 1982;64:536-541.) Prepatellar bursa (I) Patellar retinaculum (II) Iliotibial tract (I) Lateral meniscus Joint capsule (III) Popliteus tendon (III) Popliteus Fibular head Arcuate ligament (III) Ligament of Wrisberg Oblique popliteus ligament LCL (III) Fabellofibular ligament (III) Biceps tendon Common peroneal nerve Patella Fat pad Anterior and posterior cruciate ligaments I - First layer II - Second layer III - Third layer (91%) of cadaveric specimens de- spite the overall variability noted in the remainder of the posterolateral complex. Many authors have stressed the importance of this ligament in maintaining posterolateral stability and function. Arcuate Ligament Spanning the junction from the fibular styloid process to the lateral femoral condyle, the arcuate liga- ment reinforces the posterolateral capsule. 11,12 Possessing both a medi- al and a lateral limb, this Y-shaped ligament is composed of the lateral portion of the popliteus tendon and the fascial condensation over the posterior surface of the popliteus muscle. The fabellofibular, or short collateral, ligament may also be pres- ent in conjunction with the arcuate ligament, providing a variable con- tribution to overall posterolateral stability. 6,12 Biceps Femoris The biceps femorisÑconsisting of a long and a short head with nu- merous armsÑcourses posterior to the iliotibial band and inserts pri- marily on the fibular head. It also sends strong attachments to the ilio- tibial bands, GerdyÕs tubercle, the LCL, and the posterolateral cap- sule. 1,12 In conjunction with the ilio- tibial band, the biceps femoris acts as a powerful external rotator of the tibia, as well as a strong dynamic lateral stabilizer of the knee. 12 In- jury to the biceps femoris complex frequently occurs in PLRI. Additional Structures The middle third of the capsular ligament blends with the capsule over the LCL and inserts slightly posterior to GerdyÕs tubercle. 11,12 Although this structure is most like- ly a secondary restraint to varus stress, DeLee et al 1 have reported a 33% incidence of injury to this liga- ment in acute PLRI. The lateral head of the gastrocnemius provides varying degrees of posterolateral stability and blends with the arcu- ate ligament. 12 The lateral menis- cus, which is stabilized by a portion of the popliteus tendon as well as the capsule, also contributes to lat- eral stability by adding concavity to the lateral tibial plateau. 12 The pos- terior capsule is attached proximally to the lateral femoral condyle and is covered by the lateral gastrocne- mius and plantaris. The distal cap- sular attachment is complex; the popliteus muscle and aponeurosis blend into the tibial attachment lat- eral to the PCL, whereas the distal corner is stabilized to the fibula by the arcuate, popliteofibular, and fabellofibular ligaments. 12 Biomechanics The lateral ligamentous structures of the knee differ from the medial structures in that the lateral struc- tures are stronger and more sub- stantial and are subjected to greater forces during the normal gait cycle. During the stance phase, the medial compartment is under compression, while the lateral structures are un- der tension secondary to the relative position of the normal mechanical axis of the lower extremity, which lies slightly medial to the center of the knee. The structures of the posterolat- eral corner function primarily to resist posterior translation as well Frank S. Chen, MD, et al Vol 8, No 2, March/April 2000 99 Plantaris muscle Medial head of gastrocnemius muscle Lateral head of gastrocnemius muscle Fabella Arcuate ligament Fabellofibular ligament Medial collateral ligament Lateral inferior geniculate artery Popliteus muscle Medial head of gastrocnemius muscle Lateral head of gastrocnemius muscle Semimembranosus muscle Femur Patella Prepatellar bursa Patellar retinaculum Apex of fibular head Biceps tendon Iliotibial tract Common peroneal nerve Figure 2 Oblique view of the posterolateral aspect of the knee after removal of the two superficial layers. as external and varus rotation of the tibia. The posterolateral structures, however, act in concert with the PCL in providing this overall stabil- ity. The complex structure of the knee does not allow for pure rota- tional and translational motions; consequently, abnormal pathome- chanics usually result from a com- bination of coupled rotation and translation. 5,12 Cadaveric studies have been conducted in which sectioning of the posterolateral structures and the PCL was performed to deter- mine their individual effects on various motions in the knee. The findings of these studies will be briefly summarized. Anterior-Posterior Translation Sectioning of the posterolateral structures alone results in an in- crease in posterior translation of the lateral tibial plateau primarily at 30 degrees of flexion, with a minimal increase at 90 degrees of flex- ion. 5,13,14 However, when the pos- terolateral structures and the PCL are sectioned, increases in posterior translation of both the medial and the lateral tibial plateaus are ob- served at both 30 and 90 degrees of knee flexion. 13-15 Thus, the postero- lateral structures appear to provide resistance to posterior tibial transla- tion primarily at lesser degrees (e.g., 30 degrees) of flexion, whereas the PCL provides secondary resis- tance throughout a full range of motion. Varus-Valgus Rotation Sectioning of the PCL alone does not affect varus rotation of the tibia. Isolated sectioning of the postero- lateral complex, primarily the LCL, results in increased varus rotation from 0 to 30 degrees of flexion, with the maximal increase observed at 30 degrees. 5,14,15 Combined section- ing of the PCL and posterolateral structures results in increased varus rotation (as much as 19 degrees) of the knee at all angles of flexion, with the maximal increase observed at 60 degrees. 14,15 Thus, the pos- terolateral structures act as a re- straint to varus rotation primarily at lesser degrees of knee flexion (maximal restraint at 30 degrees). Internal-External Rotation Isolated sectioning of the poste- rolateral structures has been shown to result in increased external rota- tion of the lateral tibial plateau when subjected to a posteriorly directed force, with maximal exter- nal rotation observed at 30 degrees of flexion. Insignificant increases in external rotation are observed at 90 degrees of flexion with an intact PCL. 5,14,15 Combined sectioning of the PCL and posterolateral struc- tures results in an increase in exter- nal rotation of the tibia on the femur at all angles of knee flexion, with the maximal increase (as much as 20 degrees of external rotation) noted at 90 degrees. 14,15 Thus, the posterolateral structures appear to provide maximal re- straint to tibial external rotation primarily at lesser degrees of knee flexion and also play an important overall role in coupled tibial exter- nal rotation in conjunction with the PCL. It should be noted, however, that isolated sectioning of the PCL does not result in increased tibial external rotation at any flexion angle. Thus, in the presence of clinically increased tibial external rotation, an injury to the posterolat- eral complex should be suspected. Intra-articular Pressures Sectioning of both the posterolat- eral structures and the PCL results in increased medial and lateral compartment pressures, as well as increased patellofemoral pressures secondary to a Òreverse MaquetÓ effect. These elevated compartment pressures may predispose to the de- velopment of early degenerative joint disease. 16 Sectioning of the LCL and posterolateral structures has also been shown to result in increased stresses on the anterior cruciate ligament (ACL) with inter- nal rotation, as well as on the PCL with external rotation. 17 Mechanism of Injury Most cases of PLRI are secondary to trauma, with approximately 40% occurring as a result of sports in- juries. It has been suggested that certain factors may predispose to PLRI, such as genu varum, congen- ital ligamentous laxity, and various developmental factors (e.g., recur- vatum, epiphyseal dysplasia). 12 The usual mechanism of injury involves hyperextension with a varus moment combined with a twisting force. With the knee in extension, the posterolateral cap- sule is the principal restraint to injury. A posterolaterally directed blow to the medial tibia with the knee in extension is the most com- mon mechanism of injury. 12 This results in forceful hyperextension with simultaneous external rota- tion of the knee. Much less com- monly, these injuries occur due to noncontact hyperextension and external rotation. Sudden upper leg and body deceleration with the lower leg fixed may result in injury to the posterolateral structures. 12 It is important to note, however, that all of these mechanisms can result in injury to the cruciate ligaments and other knee structures, account- ing for the high incidence of com- bined injury patterns. Clinical Presentation In cases of acute PLRI, patients usu- ally describe a history of trauma and present with pain over the posterolat- eral aspect of the knee. Patients may also report motor weakness as well as numbness and paresthesias in the Posterolateral Rotatory Instability of the Knee Journal of the American Academy of Orthopaedic Surgeons 100 lower leg secondary to an associated peroneal nerve palsy. This has been reported to occur in as many as 30% of patients with acute PLRI. 12 After the initial pain and swell- ing of acute injuries have subsided, patients may also report instability, primarily with the knee in extension (e.g., during toe-off), such that the knee buckles into hyperexten- sion. 12,15 This functional instability is characteristic of patients with chronic PLRI as well. Patients may have difficulty in ascending and descending stairs, as well as with cutting activities requiring lateral movement. In addition to their functional knee instability, patients with chronic PLRI may describe pain localized along the lateral joint line. Patients may also present with gait abnormalities and may describe symptoms secondary to associated ligamentous injuries. 12,15 Physical Examination Physical examination should in- volve an overall inspection of the limb, including gait pattern, limb alignment, and mechanics. Pa- tients typically exhibit gait abnor- malities characterized by a varus thrust at the knee coupled with knee hyperextension in stance phase. 12,15 Patients may require the use of shoe lifts or high-heeled shoes to maintain ankle equinus and prevent knee hyperextension. 12 Patients often maintain the tibia in internal rotation while ambulating to prevent subluxation, as the knee is more unstable in external rota- tion. In addition, patients may exhibit varus malalignment with the mechanical axis shifted medially, resulting in an increased adduction moment of the knee that further exacerbates their symptoms. This overall varus alignment is an im- portant factor that may lead to fail- ure of operative treatment if not corrected at the time of surgery. Patients may present with an abrasion or an area of ecchymosis over the anteromedial tibia after recent trauma. One should have a high index of suspicion for knee dislocations in cases of multiple lig- amentous injuries. A careful neuro- logic examination, focusing on the peroneal nerves, should be per- formed. In addition, there are numerous specific tests that are valuable in the diagnosis of sus- pected PLRI. These individual tests are most useful when used in con- junction with clinical suspicion and other physical examination find- ings. Assessment of an awake pa- tient may be difficult; in many instances, especially with acute injuries, examination under anes- thesia may be helpful. Anterior-Posterior Translation In cases of isolated posterolateral injury, patients will demonstrate evidence of increased posterior tib- ial translation on the femur only at 30 degrees of flexion. However, in cases of combined posterolateral and PCL injury, patients will have increased posterior tibial translation at both 30 and 90 degrees of flexion. A quadriceps active test should then be performed to further assess the integrity of the PCL. This test is performed by having the patient actively contract the quadriceps with the knee flexed 70 degrees and the foot fixed. Anterior translation of the tibia from its posteriorly sub- luxated position is observed with PCL deficiency. Varus-Valgus Rotation (Adduction Stress Test) Combined LCL and posterolat- eral injuries will result in increased varus opening at both 0 and 30 de- grees of flexion, with the maximal increase at 30 degrees. With the patient lying supine and the knee flexed 20 to 30 degrees, a varus or adduction force is then applied to the leg with gentle internal rotation of the tibia while supporting the thigh. Opening of the lateral com- partment is indicative of injury to the posterolateral corner and corre- lates with injury to the LCL and the arcuate ligament. 18 A large degree of varus laxity in full extension may indicate combined injuries of the posterolateral corner, the PCL, and possibly the ACL as well. External-Rotation Recurvatum Test This test is performed with the patient supine (Fig. 3). The examiner grasps the great toes of both feet simultaneously and lifts the lower limbs off the examining table. Posi- tive findings indicative of postero- lateral injury and instability include hyperextension (recurvatum) of the knee, external rotation of the tibia, Frank S. Chen, MD, et al Vol 8, No 2, March/April 2000 101 Figure 3 Demonstration of recurvatum and relative tibia vara at the knee on the external rotational recurvatum test suggests posterolateral instability. (Adapted with permission from Hughston JC, Norwood LA Jr: The posterolateral drawer test and external rotational recurvatum test for pos- terolateral rotatory instability of the knee. Clin Orthop 1980;147:82-87.) and increased varus deformity of the knee. The sensitivity of this test, as reported in the literature, ranges from 33% to 94%. 1,3 Posterolateral Drawer Test This test is performed with the patient supine with the hip flexed 45 degrees, the knee flexed 80 de- grees, and the tibia in 15 degrees of external rotation. With the foot fixed, pressure is applied to the tibia in a similar fashion to the posterior drawer test. Lateral tibial external rotation and posterior translation relative to the lateral femoral con- dyle are indicative of injury to the posterolateral structures. 19 This test is not specific for PLRI, and its diag- nostic sensitivity is variable (report- edly as high as 75%). 1,3 Tibial External Rotation Test This test is performed at both 30 and 90 degrees of knee flexion with the patient either prone or su- pine. 15,20 The degree of external rotation of the foot relative to the axis of the femur is evaluated while palpating the tibial plateau (Fig. 4). In cases of PLRI, the lateral plateau moves posteriorly. In anteromedial rotatory instability, the medial plateau moves anteriorly. A differ- ence in external rotation of more than 10 degrees between the nor- mal and the affected side is consid- ered evidence of a pathologic con- dition. With isolated posterolateral injury, an increase in external rota- tion compared with the contralater- al limb is noted only at 30 degrees; an increase at both 30 and 90 de- grees is indicative of a combined posterolateral and PCL injury. 15,20 Posterolateral External Rotation Test This test is a combination of the posterolateral drawer and external rotation tests and is performed at both 30 and 90 degrees of knee flex- ion as a coupled force of posterior translation and external rotation of the tibia is applied (Fig. 5). Postero- lateral subluxation of the lateral tib- ial plateau only at 30 degrees is indicative of isolated PLRI (corre- lated with injuries to the LCL and the lateral head of the gastrocne- mius). Subluxation at both 30 and 90 degrees is indicative of com- bined PLRI and PCL injury. 18 Reverse Pivot-Shift Test With the patient lying supine, a valgus stress is applied to the tibia while bringing the knee from 90 degrees of flexion to full extension with the foot in external rotation. This test is positive for PLRI if there is a palpable shift or jerk as the lat- eral tibial plateau (which is sublux- ated posteriorly in flexion) reduces with extension. 18 This test is not specific for PLRI; it has been reported to be positive in 11% to 35% of nor- mal, asymptomatic subjects. 12,21 Positive findings may be correlated with generalized ligamentous laxity and are significant only if the symp- toms are reproduced. Other Clinical Tests Other diagnostic tests described for the diagnosis of PLRI include the dynamic posterior shift test and the standing apprehension test. The latter is performed with the patient slightly flexing the knee while bearing weight on the affected leg. Increased internal rotation of the lateral femoral condyle relative to the fixed tibial plateau combined with the subjective experience of Ògiving wayÓ is considered to be 100% sensitive for the presence of PLRI. 22 Radiologic Evaluation Standard plain radiographs (ante- roposterior and lateral views) of the knee in cases of suspected injury to the posterolateral complex may show a proximal fibular tip avulsion or occasionally a fibular head frac- Posterolateral Rotatory Instability of the Knee Journal of the American Academy of Orthopaedic Surgeons 102 Figure 4 The tibial external rotation test (supine). Excessive external tibial rotation as well as posterior translation of the lateral tibial plateau is noted in cases of PLRI. (Adapted with permission from Loomer RL: A test for knee posterolateral rotatory instability. Clin Orthop 1991;264:235-238.) ture. 1,12 Avulsion of GerdyÕs tuber- cle may also be observed secondary to iliotibial band injury. 12 This must be distinguished from a Segond frac- ture, which is indicative of lateral capsular avulsion as a result of ACL disruption. In cases of more severe injury with associated ligamentous disruption, additional findings, such as tibial plateau fractures or even knee dislocation, may be seen. In cases of chronic PLRI, evidence of patellofemoral or tibiofemoral de- generative changes may be ob- served. Most commonly, involve- ment of the lateral compartment is more advanced than that of any other compartment. Lateral tibial osteophytes may be seen, along with evidence of lateral compartment involvement, such as joint-space narrowing and subchondral sclero- sis of the tibial plateau. Varus stress radiographs may be helpful in determining the degree of injury. A constant force is placed on the knee in the frontal and sagit- tal planes to demonstrate both the direction and the degree of instabil- ity. In addition, full-length weight- bearing radiographs of both lower extremities may be helpful in deter- mining overall limb alignment, es- pecially in cases of chronic PLRI. Valgus osteotomies, if needed, can then be planned and templated in anticipation of correction of varus limb alignment, along with surgical reconstruction of the posterolateral complex. Magnetic resonance imaging is an excellent diagnostic tool in the evaluation of posterolateral injuries, providing visualization of individ- ual posterolateral structures. A bone contusion on the anteromedial femoral condyle indicative of pos- terolateral injury is frequently ob- served. Magnetic resonance imag- ing is also useful for evaluation of the cruciate ligaments and other lig- amentous and soft-tissue structures in the knee to determine the pres- ence of associated injuries. Treatment The natural history of isolated PLRI has not yet been clearly delin- eated. The results of early studies indicated that most professional and recreational athletes who sus- tain isolated posterolateral injury have no evidence of impaired func- tion initially. 3,12 However, it has been postulated that there may be a predisposition to early degenera- tive joint disease. It is also believed that there is an increased degree of disability when a combined liga- mentous injury pattern exists. The role of early surgical intervention is still unclear. However, surgical repair or reconstruction of the pos- terolateral structures should be performed before degenerative changes develop in the knee joint. In general, nonoperative man- agement should be prescribed for patients with mild instability with- out significant symptoms or func- tional limitations. These patients may be treated with a brief period of initial immobilization (2 to 4 weeks), followed by an extensive rehabilitation program that in- cludes protected range-of-motion and quadriceps-strengthening exer- cises. Sport-specific drills may be begun and gradually progressed as strength increases. Baker et al 3 ob- served that 14 of 31 patients with mild instability were able to return to their preinjury level of athletic participation with nonoperative treatment. 3 Currently, the indications for surgical treatment of PLRI of the knee include symptomatic instabil- ity with functional limitations as confirmed by significant objective physical findings (e.g., 2+ or greater varus opening at 30 degrees or a positive external-rotation recurva- tum, tibial external rotation, or pos- terolateral external-rotation test). In general, surgical repair is recom- mended within the first 2 weeks, if possible. Results of chronic PLRI repair have been shown to be infer- ior to those for acute PLRI. In addi- tion, simultaneous evaluation and treatment of associated ligamentous injuries is mandatory. OÕBrien et al 23 noted that the most common Frank S. Chen, MD, et al Vol 8, No 2, March/April 2000 103 Figure 5 The posterolateral external rotation test at 30 degrees. Left, Patient is supine with the knee flexed at 30 degrees and in neutral rotation. Center, A coupled force of pos- terior translation and external rotation is applied to the tibia while palpating the postero- lateral aspect of the knee. Right, Abnormal posterolateral subluxation of the lateral tibial plateau indicative of PLRI is shown by the arrow. (Adapted with permission from LaPrade RF, Terry GC: Injuries to the posterolateral aspect of the knee: Association of anatomic injury patterns with clinical instability. Am J Sports Med 1997;25:433-438.) identifiable cause of ACL recon- struction failures was unrecognized and untreated concomitant PLRI. In cases of combined injury pat- terns, reconstruction of the ACL or PCL should be performed either prior to or concurrently with repair or reconstruction of the posterolat- eral structures. In addition to addressing con- comitant ligamentous injuries, it is also important to correct any varus knee alignment that may be pres- ent. A valgus osteotomy of the proximal tibia with distal advance- ment of the iliotibial band with a bone block can be performed. 24 This should be done either prior to or at the time of surgical recon- struction of the posterolateral struc- tures. Uncorrected varus lower- limb alignment may lead to failure of the posterolateral reconstruction secondary to chronic repetitive ten- sile stresses and stretching of the surgically reconstructed structures. In general, the common goal of the numerous surgical procedures described is to restore stability of the knee by resisting varus stress, posterior tibial translation, and tib- ial external rotation. Surgical op- tions can be divided into four main categories: primary repair, augmen- tation, advancement, and recon- struction. Surgical Approach Despite the numerous surgical techniques described for posterolat- eral repair and reconstruction, no single universal surgical approach has been adopted. In general, a lat- eral skin incision is made with the knee slightly flexed and is carried from the midlateral aspect of the distal thigh along the iliotibial band, extending distally past GerdyÕs tubercle. Terry and LaPrade 11 re- cently described a surgical approach consisting of three fascial incisions along with a capsular incision for exposure of the posterolateral struc- tures. The first fascial incision bisects the iliotibial band; the sec- ond is made between the posterior border of the iliotibial band and the short head of the biceps femoris; and the third is made along the pos- terior border of the long head of the biceps femoris. The capsular inci- sion is made along the anterior bor- der of the LCL. Direct Primary Repair Direct repair of the posterolateral structures should be attempted ini- tially if the tissues are of good quali- ty, in order to restore both the ten- sion in the popliteal complex and the overall stability provided by the posterolateral corner. 12,24-26 Primary repair may be possible in many acute cases, but in chronic cases in which extensive scarring precludes the definition of individual struc- tures, direct repair is usually not possible. Repair of the posterolat- eral structures should be performed with the knee in approximately 60 degrees of flexion and the tibia in either neutral or slight internal rota- tion. 12,25 Disruption of the tibial attach- ment of the popliteus can be re- paired by reattaching the popliteus tendon by means of either sutures or a cancellous screw to the postero- lateral tibia 24,25 (Fig. 6). Avulsion of the femoral insertion of the popli- teus usually occurs along with avul- sion of the femoral origin of the LCL; these structures can be reat- tached to an osseous bed in the lat- eral femoral condyle by means of sutures through transosseous drill holes. 12,25 Disruption of the fibular attachment of the popliteofibular ligament can be addressed by teno- desing the popliteus tendon to the posterior aspect of the fibular head and reinforcing it with the fabello- fibular ligament (if present). 24,25 Avulsions of the LCL and the arcu- ate ligament from the fibular styloid process can also be repaired through transosseous drill holes in the fibu- lar head. 12 Augmentation of Posterolateral Structures Augmentation of the posterolat- eral structures is recommended when the popliteus and its related structures are attenuated and the quality of the primarily repaired tis- sues is tenuous. 24,25 In this instance, the tibial attachment of the popliteus can be augmented with a strip of the iliotibial band that is left attached distally to GerdyÕs tubercle. The ilio- tibial band strip is passed from ante- rior to posterior through a drill hole in the proximal tibia and then sutured to the popliteus tendon 24,25 (Fig. 7, A). When the popliteofibular ligament is disrupted and irrepa- rable, a central slip of the biceps ten- don can be utilized to augment and reconstruct this structure. While leaving its distal attachment to the fibular head intact, the central slip of the biceps is sutured to the posterior Posterolateral Rotatory Instability of the Knee Journal of the American Academy of Orthopaedic Surgeons 104 Figure 6 Direct repair of popliteus tendon injury. Disruption of the tibial attachment of the popliteus or the popliteus muscle- tendon junction may be treated by tenode- sis of the popliteus tendon to the posterolat- eral aspect of the proximal tibia. (Adapted with permission from Maynard MJ, Warren RF: Surgical and reconstructive technique for knee dislocations, in Jackson DW [ed]: Reconstructive Knee Surgery. New York: Raven Press, 1995, pp 161-183.) fibula, passed under the remaining biceps, and secured to the lateral femur 24 (Fig. 7, B). Advancement of Posterolateral Structures Arcuate complex advancement has been recommended by numer- ous authors for cases in which the posterolateral structures are insuffi- cient or incompetent for direct pri- mary repair. 1,3,4,26,27 Advancement of the posterolateral complex (i.e., LCL, popliteus muscle and tendon, posterolateral capsule, arcuate liga- ment, and lateral gastrocnemius tendon) can be performed either proximally or distally back to its anatomic location on the femur or tibia. In cases of chronic PLRI with an LCL of normal integrity, proxi- mal advancement of the posterolat- eral structures can be performed if the popliteofibular ligament is intact. Superior and proximal advancement of the posterolateral complex is performed in line with the LCL into a trough in the distal femur (Fig. 8). Tensioning is per- formed with the knee in 30 degrees of flexion and neutral tibial rota- tion. It has been suggested that recession of the popliteus at the femoral insertion will restore stabil- ity and tension in the posterolateral complex, but this technique alone is ineffective in cases of injury to the distal structures, such as the popli- teofibular ligament. 12 Numerous authors have reported good results with advancement of the arcuate complex. DeLee et al 1 reported that 8 (73%) of 11 patients with acute PLRI had good objective and functional results at the 7.5-year follow-up examination, with no evi- dence of degenerative joint disease and no revisions. Hughston and Jacobson 4 reported that of 19 pa- tients with isolated chronic PLRI treated with proximal arcuate com- plex advancement combined with distal primary repair, 12 (63%) had good functional results at 4 years. Noyes and Barber-Westin 27 reported on 21 patients with combined PLRI and ACL or PCL injuries treated with proximal advancement of the posterolateral structures, noting good functional results at 42 months in 14 (67%), with a failure rate of 9% (2 patients). The disadvantage of proximal arcuate complex advance- ment lies in the fact that the inser- tion sites of the popliteus and LCL are shifted anterior to the center of knee rotation, which theoretically may lead to stretching and eventual failure of the repair over time. Surgical Reconstruction Reconstruction of the posterolat- eral complex is performed in cases of acute PLRI when the tissues are Frank S. Chen, MD, et al Vol 8, No 2, March/April 2000 105 Figure 7 A, Augmentation of the attenuated tibial attachment of the popliteus tendon can be performed by using a portion of the iliotibial band passed from anterior to posterior through a bone tunnel in the proximal tibia. (Adapted with permission from Maynard MJ, Warren RF: Surgical and reconstructive technique for knee dislocations, in Jackson DW [ed]: Reconstructive Knee Surgery. New York: Raven Press, 1995, pp 161-183.) B, A central slip of the biceps is used to reconstruct the popliteofibular ligament. The central slip is tubularized, sutured to the posterior fibula, and then passed under the biceps tendon and subsequently secured to the lateral femoral condyle. (Adapted with permission from Veltri DM, Warren RF: Operative treatment of posterolateral instability of the knee. Clin Sports Med 1994;13:615-627.) A B Iliotibial graft secured to popliteus tendon Figure 8 Proximal arcuate complex advancement. The structures of the pos- terolateral region are advanced en bloc in line with the LCL into a bone trough in the lateral femoral condyle to restore tension in the posterolateral complex. (Adapted with permission from Hughston JC, Jacobson KE: Chronic posterolateral rotatory insta- bility of the knee. J Bone Joint Surg Am 1985;67:351-359.) Popliteus tendon Lateral capsular ligament Arcuate ligament complex Fibular collateral ligament Tendon of lateral head of gastrocnemius irreparable or in symptomatic pa- tients with chronic PLRI. In cases of chronic PLRI with a deficient LCL, graft reconstruction of both the LCL and the surrounding posterolateral structures is recommended. Recon- struction of the LCL restores the pri- mary restraint to varus stress and replaces the tensile-bearing tissues in the lateral aspect of the knee. This can be performed by using numerous techniques and grafts, including Achilles tendon allograft and patellar tendon autograft or allograft. 17,24-31 A central slip of the biceps tendon can also be used to reconstruct the LCL; the distal inser- tion of the biceps is left intact while a central slip is tubularized, brought proximally, and secured on the lat- eral femoral condyle near the origin of the LCL 24 (Fig. 9, A). Plication or advancement of the residual pos- terolateral structures to control ex- ternal rotation can be performed if the tissues are of sufficient quality. Noyes and Barber-Westin 28 re- ported significant subjective im- provement in symptoms and func- tion at the 42-month follow-up of 21 patients with chronic PLRI who had been treated with LCL recon- struction with use of an Achilles tendon allograft combined with either plication of the posterolateral structures to the allograft or proxi- mal advancement of these struc- tures on the femur. Sixteen (76%) patients had good to excellent func- tional results. Failure of the recon- struction occurred in only 2 pa- tients (10%). Clancy et al 29 have described bi- ceps tenodesis for advancement and tensioning of the posterolateral structures. The entire biceps ten- don is transferred anteriorly to the lateral femoral epicondyle while leaving the distal insertion intact (Fig. 9, B). The proposed advan- tages of this technique are that the LCL is recreated while the arcuate complex is tightened. In vitro ca- daveric studies have shown that biceps tenodesis at a fixation point 1 cm anterior to the LCL femoral origin is effective in decreasing external rotation and varus laxity at up to 90 degrees of knee flexion. 30 Clancy et al 29 reported good func- tional results in 90% of a small num- ber of patients at 2-year follow-up, including maintenance of stability and return to preinjury level of ac- tivity; no notable loss of hamstring strength was observed. However, a disadvantage of this technique is that the popliteus and popliteofibular lig- aments are not anatomically re- produced. Because the biceps is brought anterior to its normal func- tional axis, the normal biomechanical advantage and dynamic stabilizing effect of this muscle are disrupted. The tissue quality of the advanced posterolateral structures may also be tenuous. In vitro studies have shown that tenodesis at a fixation point other than 1 cm anterior to the LCL femoral origin results in a Ònon- isometricÓ graft position that does not reduce external rotation or varus stress at any degree of flexion. 30 Salvage posterolateral reconstruction after a failed biceps tenodesis proce- dure may be quite difficult. In cases of chronic PLRI with a deficient LCL in which the postero- lateral structures are insufficient for advancement, primary recon- struction of the entire LCL and pos- terolateral complex is necessary. An Achilles tendon allograft, patel- lar tendon autograft or allograft, or free semitendinosus autograft passed through a tibial tunnel just below GerdyÕs tubercle and a tun- nel in the lateral femoral condyle can be used to reconstruct the popliteus. 29 This, however, does Posterolateral Rotatory Instability of the Knee Journal of the American Academy of Orthopaedic Surgeons 106 Figure 9 A, Reconstruction of the LCL utilizing a central slip of the biceps tendon, which is tubularized (as shown) and then secured proximally on the lateral femoral condyle while leaving the remainder of the biceps attachment intact. (Adapted with permission from Veltri DM, Warren RF: Operative treatment of posterolateral instability of the knee. Clin Sports Med 1994;13:615-627.) B, Biceps tenodesis. The entire biceps tendon is trans- ferred anteriorly and secured to the lateral femoral condyle, thereby recreating the LCL and restoring tension to the residual posterolateral structures. (Adapted with permission from Clancy WG, Meister K, Craythorne CB: Posterolateral corner collateral ligament reconstruction, in Jackson DW [ed]: Reconstructive Knee Surgery. New York: Raven Press, 1995, pp 143-159.) A B Biceps tendon