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 the LCL.

What is the PCL?

The posterior cruciate ligament (PCL) acts as a partner to the ACL. Both tough bands of tissue, the PCL and the ACL connect the thighbone (femur) and the large bone in the lower leg (tibia) at the knee joint. These two ligaments work together to stabilize the knee and protect it from front-to-back and back-to-front impacts by forming an “X” pattern of support across the knee joint.

In this partnership, the PCL is responsible for preventing the lower leg from slipping too far back (in relation to the upper leg), particularly while the knee is bent.

What is the LCL?

Like the ACL and the PCL, the MCL and the lateral collateral ligament (LCL) work together to stabilize the knee joint. The collateral ligaments are located on the outside of the knee and help control the sideways movement of the knee. The LCL is located on the outside of the knee, while the MCL is located on the inside of the joint.

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 is when the ligament is mildly stretched. This injury may not even be felt and typically does not noticeably affect the stability of the knee.

Grade II PCL Injury

A Grade II injury is considered moderate, as the ligament is partially torn or is stretched so much the ligament is loose and the knee is a bit unstable. Grade II injuries typically result in the knee buckling or giving out during some activities.

Grade III PCL Injury

A Grade III injury is when the PCL is separated from one or both of the bones it anchors or is completely torn. This severe injury typically is caused by a significant impact, which often injures other parts of the knee, such as the ACL or the 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.