The posterior cruciate ligament (PCL) is one of the two cruciate ligaments that stabilise the knee joint. 

Gross anatomy

The ligament is intracapsular but extrasynovial and is, on average, 38 mm in length and 13 mm in width. Due to its shorter and thicker morphology it is considerably stronger than the anterior cruciate ligament (up to about double in thickness)⁵.

The posterior cruciate ligament arises from anterolateral surface of the medial femoral condyle within the notch. It extends posterolaterally to the posterior intercondylar surface of the tibial plateau, about 1 cm to the joint line (with its anterior border defined by the posterior horn of the medial meniscus)⁴. It contains two fibre bundles - a larger anterolateral and a smaller posteromedial bundle, which blend at the point of insertion ^1,4.

Relations

• Anterolateral: anterior cruciate ligament passes lateral and curves around it

• Posterior: Immediately posterior lies the oblique popliteal ligament (inferior) and posterior meniscofemoral ligament (superior, posterior to PCL origin). The popliteal artery, popliteal vein and tibial nerve are also posterior

Arterial supply

• middle genicular artery ⁴

Innervation

• tibial nerve

Variant anatomy

• cruciate ligament dysplasia

Function

During flexion, the anterolateral band becomes tight, whereas the posteromedial bundle tightens during extension ¹ and the posterior cruciate ligament as whole acts to resist anterior translation of the femur on the tibia, and posterior translation of the tibia relative to the femur². While in flexion and weight-bearing (such as walking downhill), PCL is the key stabiliser of the knee joint. During extension, the PCL limits anterior rolling of the femur on the tibia.⁵

Radiographic features 

MRI

The two bundles cannot be separately identified on MRI and the PCL appears as intensely hypointense. The apex of the posterior cruciate ligament is susceptible to magic angle effect (an MR artifact) and a high signal can be seen in this area but it is of no pathological significance ². 

Related pathology

• PCL tear

• double PCL sign

• Reverse segond fracture