Most people are familiar – some intimately – with their knees’ ACLs (anterior cruciate ligaments) and MCLs (medial collateral ligaments). As the two most common ligaments in the knee that are injured every year, the ACL and MCL get a lot of attention. There are, however, two other ligaments that play important roles in the knee joint: the PCL and LCL.

What is the PCL?

The posterior cruciate ligament (PCL) partners with the anterior cruciate ligament (ACL). Both are strong tissue bands connecting the thighbone (femur) to the tibia at the knee joint. They work together to stabilize the knee. Additionally, they protect against front-to-back and back-to-front impacts. This creates an “X” pattern of support across the knee joint.

In this partnership, the PCL plays a crucial role in stabilizing the knee. Specifically, it prevents the lower leg from sliding excessively backward relative to the upper leg. This function is especially important when the knee is bent. By maintaining this stability, the PCL ensures proper alignment and movement, enhancing overall knee function.

What is the LCL?

The MCL and LCL, like the ACL and PCL, are crucial for stabilizing the knee joint. These collateral ligaments are positioned on the knee’s outer sides. Specifically, the LCL is situated on the outer aspect, whereas the MCL is found on the inner side of the joint. Both ligaments are essential for controlling sideways movements of the knee, ensuring its stability and proper function.

PCL Injuries: Sprains and Tears

A PCL injury occurs when the ligament is overly stretched or torn by an unusual movement or force. According to Harvard Health Publishing, the PCL is most commonly injured during automobile accidents and in sports when athletes fall forward on a bent knee.

All ligament injuries are considered “sprains” – even if the ligament is technically torn. As with any other ligament injury, PCL injuries fall into three categories: Grade I Sprains, Grade II Sprains and Grade III Sprains.

Grade I PCL Injury

A Grade I injury involves a mild stretching of the ligament. In many cases, this injury may go unnoticed. Typically, it does not significantly impact knee stability. However, it’s essential to address even minor injuries to prevent further issues.

Grade II PCL Injury

A Grade II injury is classified as moderate. This type of injury occurs when the ligament is either partially torn or excessively stretched, leading to looseness and instability in the knee. Consequently, the knee may buckle or give out during certain activities. Thus, it’s crucial to address Grade II injuries promptly to prevent further complications.

Grade III PCL Injury

A Grade III injury occurs when the PCL is either fully torn or completely detached from one or both of its anchor bones. This serious condition usually results from a substantial impact. Furthermore, such severe trauma often damages other knee structures, including the ACL and MCL.

Types of LCL Sprains

LCL injures are graded on the same three levels as PCL injuries, with small adjustments in terms of pain location and knee function. Also similar to Grade III PCL injuries, Grade III LCL injuries are typically accompanied by tears to the ACL or other knee injuries.

The most common causes of LCL injuries are a direct impact to the inside of the knee, landing awkwardly or poorly from a jump and changing directions quickly.

PCL Knee Injury Symptoms

PCL injuries often have such mild symptoms that a PCL tear may only be discovered while diagnosing another knee injury. Many athletes unknowingly continue to compete after a PCL injury and tend to say that their knee “just doesn’t feel right” once they do seek treatment.

PCL tear symptoms may include:

• Mild pain at the back of the knee that worsens when kneeling
• Mild swelling
• Pain in the front of the knee, particularly while running or slowing down

LCL Kneed Injury Symptoms

If you’ve injured your LCL, you’re most likely experiencing pain and swelling.

Other common LCL tear symptoms include:

• Stiffness, soreness or tenderness on the outside of the knee
• A feeling that your knee may give out while standing or walking
• Your knee catches or locks in place while you walk
• Bruising around the knee
• A reduced range of motion
• Knee pain and foot numbness

If you think you’ve suffered a PCL or LCL injury and would like to consult a knee specialist, please feel free to contact us. Our orthopedic surgeons are happy to answer any questions you may have.