Posterior cruciate ligament

At a glance

English

Posterior cruciate ligament

Latin (TA2)

Ligamentum decussatum posterius

System

Ligament

Region

Lower limb

Side

Paired, left and right

About the posterior cruciate ligament

The posterior cruciate ligament, or PCL, lies in the centre of the knee and crosses behind the anterior cruciate ligament. It takes its name from its tibial attachment at the back of the joint. Like its partner, it lies inside the fibrous capsule but is excluded from the synovial cavity by a covering of synovial membrane. It is thicker and stronger than the ACL. In quadrupeds the corresponding ligament is called the caudal cruciate ligament.

Below, the PCL is fixed behind the tibial spines, in the posterior intercondylar area, and extends a little way down onto the back of the bone, just under the articular surface. From there it climbs forwards and medially to attach to the outer surface of the medial femoral condyle, at the front of the intercondylar notch and onto its roof. It is described as two bundles: an anterolateral bundle that tightens as the knee flexes and a posteromedial bundle that tightens in extension. The meniscofemoral ligaments from the back of the lateral meniscus run close beside it, one in front and one behind.

Its job is to stop the tibia being pushed backwards under the femur, or equivalently to stop the femur sliding forwards off the front of the tibia. It is the main stabiliser of the bent knee, for example when walking downhill or descending stairs, and it also limits hyperextension and some rotation.

Typical injuries come from a blow to the front of the bent knee, such as hitting a car dashboard, or from a fall onto a flexed knee, both of which drive the tibia backwards. Doctors test it with the posterior drawer test and look for the posterior sag, in which the top of the tibia drops back when the hip and knee are held at right angles. Isolated tears often settle with physiotherapy to strengthen the quadriceps, while severe tears and combined injuries, especially of the posterolateral corner, may need reconstruction with a graft.

Attachments and function

Attaches from

The tibial posterior intercondylar area and the adjoining back of the bone just below the plateau.

Attaches to

The lateral surface of the medial femoral condyle, at the front of the intercondylar fossa.

Function

Prevents backward displacement of the tibia on the femur, stabilises the flexed knee and limits hyperextension.

Nerve supply

Posterior articular branches of the tibial nerve.

Blood supply

The middle genicular artery, through the synovial covering of the ligament.