REVIEW ARTICLE Posterolateral Corner Injuries of the Knee: Anatomy, Diagnosis, and Treatment Jonathan M. Cooper, DO,* Peter T. McAndrews, DO,* and Robert F. LaPrade, MD, PhDw injury is not repaired or reconstructed.4,13,14 In turn, graft Abstract: Injuries to the posterolateral corner of the knee failure and possible revision surgery can result in further continue to be a complex problem for orthopedic surgeons. patient morbidity. Early recognition and treatment are important factors in the A complete understanding of the anatomy and patient’s long-term outcome. To properly treat these patients, thorough physical examination combined with proper the surgeon must have a clear understanding of the anatomic imaging studies and arthroscopic evaluation will allow the relationships amongst the structures in the posterolateral knee. surgeon to make a correct diagnosis and formulate a This knowledge combined with a thorough physical examina- treatment plan. The timing of surgery is critical as it can tion and imaging studies, allows the surgeon to make the correct dictate whether an anatomic repair is possible or a diagnosis and devise an appropriate treatment plan. This article reconstruction may be required. will discuss the anatomy, diagnosis, and treatment options to improve the surgeon’s understanding of posterolateral knee APPLIED ANATOMY injuries. The senior author’s technique for anatomic reconstruc- Most authors now agree that the popliteus tendon, tion of the posterolateral corner of the knee and the rehabilita- popliteofibular ligament, and fibular collateral ligament tion protocol are described. are the most important structures for posterolateral knee Key Words: posterolateral corner, repair, reconstruction, lateral stability. These static stabilizers are of significance due to knee injuries, fibular collateral ligament, popliteofibular the convex opposing surfaces of the lateral femoral ligament condyle and lateral tibial plateau. Comprehension of the anatomy of the main static stabilizers is fundamental to (Sports Med Arthrosc Rev 2006;14:213–220) understanding their biomechanical function, appearance on magnetic resonance imaging (MRI) scans, and repair/ reconstruction at the time of surgery. osterolateral corner injuries of the knee can be very The fibular collateral ligament is the primary static Pdebilitating for patients when unrecognized or treat- stabilizer to varus opening of the knee. It is thought to be ment is delayed. In recent decades, a concerted effort has most important in preventing varus instability of the knee been made to more precisely define the anatomy, during the initial 0 to 30 degrees of knee flexion.7 The biomechanics, diagnosis, and treatment of posterolateral proximal attachment site of the fibular collateral ligament 1–12 knee injuries. Despite significant gains in our under- on the femur is in a depression slightly proximal and standing of the posterolateral knee, these injuries remain posterior to the lateral epicondyle.10 At its distal elusive and treatment continues to be controversial with attachment to the fibular head, the fibular collateral publications centered around expert opinions and case ligament is easily identified by making a horizontal series creating a limited hierarchy of evidence. The incision through the anterior arm of the long head of complex anatomy with multiple layers and fibrous the biceps femoris and entering the bursa between the attachments between local tendons, ligaments, and bones fibular collateral ligament and the biceps femoris.12 1,6 contribute to the diagnostic difficulties. The popliteus muscle and tendon complex has many Failure to recognize a posterolateral knee injury can components providing static and dynamic stabilization to cause instability during normal gait resulting in a varus- posterolateral rotation of the knee.10,15 The proximal thrust pattern. Posterolateral instability with a concurrent attachment of the popliteus tendon is in the proximal half anterior or posterior cruciate ligament tear places the of the anterior fifth of the popliteus sulcus. This is on cruciate ligament grafts at significant risk for failure average 18.5 mm from the attachment of the fibular during subsequent reconstruction if the posterolateral collateral ligament.10 As the popliteus tendon courses distally, three popliteomeniscal fascicles extend to the lateral meniscus (anteroinferior, posterosuperior, and From the *TRIA Orthopaedic Center, Bloomington; and wUniversity of posteroinferior).10 Further distal, at the musculotendi- Minnesota, Minneapolis, MN. nous junction, the popliteofibular ligament courses Reprints: Robert F. LaPrade, MD, PhD, Department of Orthopaedic laterally and distally to insert on the posteromedial Surgery, University of Minnesota, 2450 Riverside Avenue, R200, 10,15 Minneapolis, MN 55454 (e-mail: [email protected]). aspect of the fibular styloid. The popliteofibular Copyright r 2006 by Lippincott Williams & Wilkins ligament is an important stabilizer of external rotation Sports Med Arthrosc Rev Volume 14, Number 4, December 2006 213 Cooper et al Sports Med Arthrosc Rev Volume 14, Number 4, December 2006 of the knee and is composed of 2 divisions (anterior and with posterolateral knee injuries, it serves as an important posterior).16 reference for many other structures.17 It attaches to The mid-third lateral capsular ligament is a Gerdy tubercle distally. The capsuloosseous layer extends thickening of the lateral capsule of the knee and is from the region of the lateral intermuscular septum and thought to be similar to the deep medial collateral blends with the capsular arm of the short head of the complex on the medial aspect of the knee.17 Two biceps femoris on its way to attach just posterior to Gerdy components make up the mid-third lateral capsular tubercle. This creates an anterolateral sling for the ligament. The meniscofemoral component extends from knee.10,20 the femur to the meniscus, and the meniscotibial component from the meniscus to the tibia. The menisco- DIAGNOSIS OF POSTEROLATERAL KNEE tibial component is injured more frequently and often INJURIES with a bony avulsion (Segond fracture).18,19 The long head of the biceps femoris branches into 5 History and Physical Examination arms as it courses distally10,11 (Fig. 1). The 3 most A properly performed history and physical exam- important branches are the direct arm which attaches to ination with certain tests for the posterolateral knee will the posterolateral aspect of the fibular styloid, anterior guide proper diagnosis in the majority of cases. Many arm that courses lateral to the fibular collateral ligament, posterolateral knee injuries occur in combination with and lateral aponeurotic arm attaching to the poster- cruciate ligament injuries. When the diagnosis is more olateral portion of the fibular collateral ligament. The difficult, such as in cruciate or other ligament injuries, short head of the biceps femoris also consists of 5 radiographs and MRI scans are useful adjuncts for the branches.10,11 The capsular arm extends from the main physician to aid in accurate diagnosis.17 tendon of the short head to the posterolateral capsule just The history often concentrates on the mechanism of lateral to the tip of the fibular styloid. The capsular arm injury and the subsequent symptoms. The main mechan- provides a stout attachment to the posterolateral capsule, isms for injury to the posterolateral knee are a blow to the lateral gastrocnemius tendon, and the capsuloosseous anteromedial knee, contact or noncontact hyperexten- layer of the iliotibial band. The distal edge of the capsular sion, or a varus noncontact force.8 During the history, arm is the fabellofibular ligament.8,10,18,19 The fabellofib- it is important to inquire about numbness or tingling in ular ligament is tight in extension and becomes lax with the extremity or possible muscle weakness especially in increasing flexion. The anterior arm of the short head ankle dorsiflexion and great toe extension, as 15% of passes medial to the fibular collateral ligament and blends posterolateral knee injuries have associated common with the meniscotibial component of the mid-third lateral peroneal nerve injury.8 capsular ligament as it attaches to the tibia. Injury to the A complete physical examination of the extremity anterior arm of the short head of the biceps femoris is including a neurovascular examination and gait must be often recognized on coronal MRI scans avulsed with a performed in coordination with the posterolateral knee Segond fracture or a soft tissue Segond-type injury.18 examination. For each test, it is always important to The iliotibial band is an important structure in evaluate the unaffected knee to have a physiologic preventing varus opening of the knee. Because the baseline for comparison. superficial layer of the iliotibial band is seldom injured Gait is an important component of the physical examination as a patient with chronic posterolateral corner injury may display a varus thrust gait pattern. In this pattern, the lateral compartment of the knee opens at foot strike and the joint subluxes into varus. The patient may have learned to compensate for this thrust by ambulating with a flexed knee. It is important to remember that not all patients with a varus thrust gait pattern have a posterolateral knee injury. A varus thrust simply implies that medial condyle weight bearing is occurring along with separation of the lateral tibio-femoral compartment, which can also be seen in medial compartment arthrosis. The external rotation