Posterior cruciate ligament injury



The posterior cruciate ligament (PCL) is a ligament in each knee.



Works  as a counterpart to the anterior cruciate ligament (ACL). 



Ligaments are bands of tissues that connect bones, and similar to the anterior cruciate ligament, the PCL connects the femur to the tibia.


The PCL connects the posterior intercondylar area of the tibia to the medial condyle of the femur. 

Its function is to prevent the femur from sliding off the anterior edge of the tibia and to prevent the tibia from displacing posterior to the femur. 

Its configuration allows the PCL to resist forces pushing the tibia posteriorly relative to the femur.

The PCL and ACL are intracapsular ligaments lying deep within the knee joint. 


The synovial membrane wraps around them. 



The PCL attaches to the posterior portion of the tibia.



The PCL, ACL, MCL, and LCL are the four main ligaments of the knee.


It originates from the lateral edge of the medial femoral condyle, and goes at a posterior and lateral angle, toward the posterior of the tibia.

Excessive extension in the form of hyperextension causes tensile stress, on the posteromedial bundle of the PCL that leads to PCL injury.

During knee joint movement, the PCL rotates such that the anterolateral section stretches in knee flexion but not in knee extension and the posteromedial bundle stretches in extension rather than flexion.

Injuries are usually due to direct blows to the flexed knee, such as the knee hitting the dashboard in a car accident or falling hard on the knee, both instances displacing the tibia posterior to the femur.




Less frequent than anterior cruciate ligament injury.



The PCL stabilizes the articulating bones, particularly the femur and the tibia, during movement. 

Typical injury blow to the anterior proximal tibia with the knee flexed, such as tripping over a hurdle or striking the dashboard in a MVA.

Patients with posterior cruciate ligament injury should always be evaluated for other knee injuries that often occur in combination with an PCL injuries: cartilage/meniscus injuries, bone bruises, ACL tears, fractures, posterolateral injuries and collateral ligament injuries.



Grades of classification of  a PCL injury:



Grade I, the PCL has a slight tear.



Grade II, the PCL ligament is minimally torn and becomes loose.



Grade III, the PCL is torn completely and the knee can now be categorized as unstable.



Grade IV, the ligament is damaged along with another ligament housed in the knee 

Less swelling and instability than in anterior cruciate injuries.

The PCL functions to prevent movement of the tibia in the posterior direction and to prevent the tilting or shifting of the patella.



Its  laxity makes the PCL susceptible to injury during hyperflexion, hyperextension, and in a mechanism known as a dashboard injury.



Ligaments are viscoelastic and can handle higher amounts of stress only when the load is increased slowly.



When hyperflexion and hyperextension occur suddenly in combination with this viscoelastic behavior, the PCL deforms or tears.



The third and most common mechanism,


 is dashboard injury mechanism: The knee experiences impact in a posterior direction during knee flexion toward the space above the tibia.



Mechanisms for injury with excessive external tibial rotation and during falls that induce a combination of extension and adduction of the tibia, or that occur while the knee is flexed.



The PCL does not heal on its own. 



It is unusual for surgery to be required. 



Treatment:  strengthening  the muscles around the knee provides adequate stability even without a functional PCL. 



With ongoing symptoms, or if there are other injuries in the knee will ligament reconstruction be required.



Ligament reconstruction is usually a graft taken from the hamstring or Achilles tendon from a host cadaver. 



The new ligament is attached to the bone of the thigh and lower leg with screws to hold it in place.



Surgery to repair the posterior cruciate ligament is controversial due to its placement and technical difficulty.



Grade I and grade II PCL injuries may heal on their own.



Physical therapy may reduce recovery times in these lesions.



For Grades III and IVPCL injuries surgery is recommended or is usually required. 


The posterior sag sign is suggestive of a posterior cruciate ligament (PCL) tear.


The sag test and posterior drawer tests are used by doctors and physiotherapists to detect injury to the PCL. 




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