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Knee

PCL Injuries

There are three bones that make up the knee joint – the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). There are two cruciate ligaments—Posterior Cruciate Ligament (PCL) and Anterior Cruciate Ligament (ACL)—inside the knee joint that cross to form an X. The PCL sits in the back of the knee joint, while the ACL sits in the front of the knee joint. Together, they help control the front-to-back motion of the knee, as well as rotation.

The PCL is one of two cruciate ligaments in the knee joint that cross to form an X. It is a vital structure that helps stabilize the knee and control its movement. The PCL is the largest and strongest ligament in the knee. It has two very distinct portions: one that goes from the back of the tibia to the roof of the femoral notch (in the thigh bone) called the anterolateral bundle, and a second smaller portion that goes to the side of the notch called the posteromedial bundle. Both bundles work together to prevent the knee from slipping backward, especially when it is bent. However, as they have different attachments, they have different primary functions, and therefore, it is necessary to reconstruct both bundles when the PCL is torn.

Recall that the PCL has two bundles: the anterolateral bundle and the posteromedial bundle. The anterolateral bundle prevents excessive front-to-back motion of the tibia while the posteromedial bundle prevents excessive rotation of the tibia.

Two important structures associated with the PCL are the meniscofemoral ligaments. These are small ligaments that can sometimes be found in the knee joint. These structures attach to the lateral meniscus and follow a similar course alongside the PCL in order to attach to the femur. One of meniscofemoral ligaments attaches in the front of the posterior cruciate ligament (Ligament of Humphrey’s) and the other attaches in the back (Ligament of Wrisberg). The anterior one is present in 30% of patients and the posterior one is found in 60% of knees. Both ligaments help the PCL and prevent the knee from slipping backwards.

Given the PCL’s size and strength, it takes a significantly traumatic injury to tear it. Consequently, a PCL tear by itself, called an isolated PCL tear, is not that common. Instead, PCL injuries are usually associated with other ligamentous injuries (MCL, LCL or ACL). Most isolated PCL tears occur as a result of an injury to the front of the knee when it is bent. Falling on a bent knee while playing sports, slipping on ice, or hitting a dashboard during a traffic accident are some common ways that the PCL is torn.

A recent epidemiologic study reported that the incidence of isolated torn PCL’s is 2 per 100,000 in the general population, with more injuries in male subjects. However, the incidence of combined PCL injuries is much higher.

Patients can present with swelling, discomfort, and pain, typically when the knee is bent. When combined injuries are diagnosed, severe instability can be present. In these cases, arteries or nerves can be compromised, and therefore, it is important to rule these injuries out.

The combination of a detailed history, comprehensive physical examination, x-rays, and an MRI (magnetic resonance imaging) is the key to a successful diagnosis of a PCL injury. Dr. Jorge Chahla and his team use stability tests as part of the physical exam, including the Posterior Drawer test, Supine Internal Rotation (IR) test, quadriceps active tests, and degree of posterior sag to properly diagnose a PCL Injury.

Because isolated PCL injuries are rare, imaging studies, such as an MRI, are important to evaluate the full extent of your injuries.

Moreover, an important thing to evaluate is the actual posterior cruciate ligament function. While it can look normal and healthy on MRI after 6 months, it can heal in an elongated position. Although it looks “normal” on MRI, it might not be functioning properly in the knee. Think of a rubber band that has been stretched and subsequently cannot return to its previous tautness. To help determine if this has occurred, one special test that is used to determine the severity of your pathology are kneeling stress x-rays. These special x-rays allow for objective quantification and diagnose (based on validated systems) of a partial, complete, or combined PCL injury with millimeter accuracy. With this information, Dr. Chahla can provide an accurate diagnosis and treatment plan.

PCL injuries can be classified into different types based on the severity and extent of the damage to the PCL fibers. The grading of severity is based on the amount of ligament disruption and the extent of knee instability present following an injury. It is important to accurately diagnose the extent of a PCL injury, as the appropriate treatment plan can vary based off the type of PCL injury that an individual has suffered.

Grade 1 PCL Sprain

This is a small partial tear of the PCL, meaning that the ligament is stretched but not completely torn. The knee may still demonstrate some stability, and conservative treatment such as rest, physical therapy, and bracing can be effective in promoting healing and restoring function.

Grade 2 PCL Sprain

This is a moderate, or near complete tear of the PCL. The ligament may be partially torn, resulting in some instability in the knee joint, although there are some fibers that remain intact. Treatment options may include physical therapy, bracing, and possibly surgery in some cases.

Grade 3 PCL Sprain

This is a complete tear of the PCL in which the ligament is no longer functional. The PCL is fully ruptured, leading to significant instability in the knee joint. Usually, this occurs with injuries to other knee ligaments (most commonly the posterolateral knee structures). Grade 3 PCL tears often require surgical intervention to repair or reconstruct the damaged ligament, followed by rehabilitation and physical therapy to regain knee stability and function.

At a Glance

Dr. Jorge Chahla

  • Triple fellowship-trained sports medicine surgeon
  • Performs over 700 surgeries per year
  • Assistant professor of orthopedic surgery at Rush University
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