The AL bundle is larger and stronger than the PM bundle. The primary function of the PCL is to restrain posterior tibial translation. The PCL and posterolateral corner act synergistically to prevent posterior tibial translation and to restrain external rotation of the tibia and varus angulation of the knee. The PCL provides more restraint to posterior tibial translation with the knee in flexion and the posterolateral corner more restraint with the knee in extension. PCL injuries are most often combined with other ligamentous injuries. Three mechanisms of PCL tear have been identified:.
The most sensitive and specific test to detect injury to the PCL is the posterior drawer test.
However, physical examination is often inconclusive as to the presence of a PCL tear, 8 as the findings may be limited by pain or quadriceps and hamstring spasm, particularly in the acute setting and with combined ligamentous injuries. Importantly, arthroscopic detection of PCL tears may be difficult through an anterior approach, especially with an intact ACL. The normal PCL is homogenously low in signal on T1 and T2-weighted sequences and demonstrates a smooth convex posterior curve 5a,6a,7a.
The meniscofemoral ligaments of Humphrey and Wrisberg, when present, may be seen anterior and posterior to the PCL, respectively. In complete midsubstance tears with an intact synovial sheath, the PCL may maintain its shape with diffusely increased signal intensity. The location of the tear and the presence of avulsed bony fragment can be identified 9a.
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Because progressive functional instability and arthritis often occur due to unrecognized posterolateral, posteromedial, or anterior instability, the structures in these regions should be carefully scrutinized for injury 10a,11a,12a. The ligament of Wrisberg is also seen just superior to the PCL small arrow. The ACL origin is depicted asterisk. The ACL is also demonstrated asterisk. The distal portion of the PCL is not depicted because of slice angle, but on contiguous images the PCL over this level was intact.
The tibial fracture fragment arrowhead is mildly elevated. Although mildly lax, the PCL demonstrates normal signal with no evidence for ligamentous injury.
MRI Web Clinic — May 2006
Hemarthrosis is demonstrated by layered blood in the anterior joint space small arrows. Hemorrhage and edema associated with a posteriorly disrupted capsule arrowheads are demonstrated deep to the medial gastronemius muscle.
An anterior tibial bone bruise is also depicted asterisk. Edema within the fibular collateral ligament short arrow is compatible with a ligament sprain. Hemorrhage and edema are present along the posteromedial capsule and posterior oblique ligaments arrowheads. The findings in 10aa indicate a combined PCL injury with associated injury of the posterolateral corner. MRI readily delineates injuries of bone, other ligaments, menisci, cartilage, capsule, tendons, and vascular structures. Indirect signs of PCL injury include bone bruises of the anterior tibia and posterior femoral condyles, indicating forced posterior displacement of the tibia with the knee flexed.
Anterior tibial articular surface and anterior femoral condyle bone bruises are often seen with a hyperextension mechanism of injury. In chronic PCL tears, the PCL typically remains in continuity between the tibia and femur but the ligament caliber is attenuated or the contour is buckled 13a. In the past the significance of PCL injuries has been understated, though studies have shown an increased incidence of arthritis in this patient population.
Medial compartment and patellofemoral joint pressures increase significantly with PCL deficiency and are magnified with a coexisting posterolateral corner injury.
The multiple ligament injured knee: a practical guide to management
Close follow-up is recommended to identify unrecognized posterolateral instability and worsening functional instability. Surgical treatment is recommended for acute PCL injuries with insertional avulsions or PCL tears with greater than 10 mm of posterior tibial displacement, associated multiple ligament injuries, or associated meniscal or chondral injuries.
Combined ACL-PCL injuries are assumed to be the result of a knee dislocation and neurovascular assessment is required.
In patients with PCL and posterolateral corner injuries, surgical repair is indicated for both structures. Outcomes after posterior cruciate ligament PCL reconstructive surgery have historically been inferior to outcomes after reconstruction of the anterior cruciate ligament ACL. As such, some surgeons may be reluctant to recommend reconstruction of the PCL.
A Practical Guide to Management
However, recent technologic advances have substantially improved PCL reconstructive surgical outcomes. View on PubMed.
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