What Is a Knee Ligament Injury?

A knee ligament injury involves damage to one or more of the four major ligaments that stabilize the knee joint:

• Anterior cruciate ligament (ACL): Prevents the tibia from sliding forward and controls rotational stability.
• Posterior cruciate ligament (PCL): Prevents the tibia from sliding backward.
• Medial collateral ligament (MCL): Stabilizes the inner knee.
• Lateral collateral ligament (LCL): Stabilizes the outer knee.

Injuries to these ligaments can range from mild sprains to complete tears and are often seen in athletes.

Symptoms of a Knee Ligament Injury

Symptoms can vary by ligament, but commonly include

• ACL: A loud “pop” when the injury takes place, rapid swelling, instability, and difficulty pivoting
• PCL: Swelling, pain, and a feeling of looseness in the knee
• MCL: Pain in the inner knee, weakness, and instability
• LCL: Pain in the outer knee, weakness, and instability

How Are Knee Ligament Injuries Diagnosed?

To diagnose a knee ligament injury, a healthcare provider will conduct a thorough exam. Depending on the suspected injured ligament, one or more tests will be done:

• Anterior/Posterior Drawer Tests, for ACL and PCL tears
• Lachman Test, for ACL tears
• Valgus/Varus Stress Tests, for MCL and LCL tears

An MRI will also be used to determine the severity of the injury, and an X-ray may be needed to rule out any fractures.

Treatments for Knee Ligament Injuries

Treatment for knee ligament injuries depends on the severity and ligament involved. For less severe cases, injuries can be resolved with rest, ice, compression, and elevation, as well as bracing to stabilize the knee and physical therapy to strengthen the surrounding muscles.

For ACL and PCL reconstructions, the ligaments are repaired using grafts to restore their function. MCL and LCL injuries often do not require surgery unless severe or combined with other injuries.