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Knee

PCL Injuries

What is the PCL?

The posterior cruciate ligament (PCL) is the largest and strongest ligament within the knee joint. It plays a crucial role in stabilizing the knee, preventing it from moving backward, particularly when bent. The PCL is composed of two distinct bundles: the anterolateral bundle and the posteromedial bundle. The anterolateral bundle stretches from the back of the tibia (shinbone) to the roof of the femoral notch (part of the thigh bone) and is responsible for limiting forward-to-backward movement of the tibia. Meanwhile, the posteromedial bundle attaches to the side of the notch and helps control excessive rotation of the tibia. Due to their different functions, reconstructing both bundles is essential when a PCL tear occurs to ensure comprehensive stability.

The meniscofemoral ligaments are smaller auxiliary ligaments sometimes found within the knee joint, attaching to the lateral meniscus and running alongside the PCL to connect to the femur. These ligaments, known as the Ligament of Humphrey (anterior) and the Ligament of Wrisberg (posterior), support the PCL in maintaining knee stability. The anterior ligament is present in about 30% of people, while the posterior ligament is found in approximately 60% of knees. Together, they assist the PCL in preventing backward slippage of the knee.

Due to its robust nature, the PCL typically requires significant trauma to become injured. Most PCL injuries are not isolated; they usually occur in conjunction with damage to other knee ligaments such as the ACL, MCL, or LCL. Common causes of isolated PCL injuries include:

  • Falling directly onto a bent knee during sports
  • Slipping and landing on a flexed knee
  • Trauma from car accidents, such as striking the knee against the dashboard

Epidemiological research has shown that isolated PCL injuries occur at a rate of about 2 per 100,000 individuals in the general population. However, the incidence of combined PCL injuries involving multiple ligaments is notably higher, particularly in male patients and athletes.

Patients with PCL injuries may experience a range of symptoms depending on the severity of the tear:

  • Swelling in and around the knee joint
  • Discomfort and pain, especially when the knee is bent
  • Reduced stability or a feeling of looseness in the knee
  • Difficulty performing activities that require knee flexion

In cases where the PCL injury is combined with other ligament damage, significant knee instability can occur. These more severe cases may also compromise surrounding structures like arteries or nerves, making immediate medical evaluation essential.

PCL injuries are classified into three main grades:

  • Grade 1 PCL Sprain: A minor partial tear.
  • Grade 2 PCL Sprain: A near-complete tear, leading to moderate instability.
  • Grade 3 PCL Tear: A complete tear rendering the ligament non-functional, often accompanied by damage to other knee ligaments (e.g., the posterolateral structures).

Medical professionals utilize various clinical tests to assess the integrity of the PCL. These include:

  • Posterior Drawer Test: The knee is bent, and backward pressure is applied to evaluate movement.
  • Posterior Sag Test: Checks if the tibia sags backward when the knee is in a specific position.
  • Quadriceps Active Test: Involves contracting the quadriceps to observe knee stability.
  • Supine Internal Rotation (IR) Test: Assesses for rotational instability.

Many isolated PCL injuries, particularly Grade 1 and Grade 2 sprains, have the potential to heal on their own due to the ligament’s protective sheath that aids in recovery. However, it is crucial to assess the ligament’s function even after apparent healing. An MRI scan may show a PCL that appears structurally intact after six months, but it may have healed in an elongated state, compromising knee stability. This situation is comparable to an overstretched rubber band that no longer regains its original tension. To confirm the functional status of the PCL, stress X-rays can be conducted to dynamically assess the ligament’s behavior under pressure.

Orthopedic surgeon Dr. Mark Cinque is a sports medicine surgeon in San Diego, California who specializes in the treatment of complex knee injuries. He has spent time training at The Steadman Clinic and Stanford Orthopaedic Surgery. He has published over 100 peer-reviewed manuscripts and has presented research internationally. He uses minimally invasive arthroscopic procedures to preserve the natural joint and reduce recovery time to accelerate his patients’ return to the activities they love.

At a Glance

Mark Cinque, MD

  • Board-certified, fellowship-trained orthopedic surgeon
  • Orthopedic Residency: Stanford University, Fellowship: The Steadman Clinic
  • Authored over 100 peer-reviewed publications
  • Learn more
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