Posterior Cruciate Ligament (PCL) Injury
An injury to a deep stabilizing ligament at the back of the knee
Quick Facts
- Type: Knee ligament injury
- Common cause: Blow to the front of a bent knee
- Classic sign: Aching, stiffness, mild instability
- Treatment: Often rehab; surgery for severe cases
Overview
The posterior cruciate ligament (PCL) is one of the four main ligaments of the knee. It sits deep within the joint, crossing behind the anterior cruciate ligament, and it prevents the shinbone (tibia) from sliding too far backward under the thighbone. The PCL is thicker and stronger than the ACL, so it tears less often.
A PCL injury is a stretch or tear of this ligament. Because the PCL has some capacity to heal and the knee can often compensate, many isolated PCL injuries are managed without surgery. Severe tears, or those combined with damage to other ligaments, may need surgical repair.
Symptoms
PCL injuries can be subtle, especially compared with ACL tears. Symptoms may include:
- Pain and swelling in the knee, often milder than other ligament injuries
- Stiffness and difficulty bending the knee
- A feeling of instability, particularly going down stairs or slopes
- Mild trouble walking or a sense the knee may give way
Some people have only modest symptoms at first and do not realize the ligament is injured until instability or aching persists.
Causes
PCL injuries usually result from a strong force driving the top of the shinbone backward while the knee is bent. Common causes include:
- Striking the knee against a car dashboard in a collision (the classic "dashboard injury")
- Falling onto a bent knee with the foot pointed down
- A direct hit to the front of the shin during contact sports
- Severe twisting or hyperextension of the knee
Risk Factors
- Participation in contact sports such as football, soccer, and rugby
- Activities with a high risk of falls onto the knee
- Motor vehicle collisions
- Prior knee injury or instability
- High-energy trauma that injures several knee structures at once
Diagnosis
A clinician examines both knees and checks how far the shinbone moves backward.
- Posterior drawer test: The examiner pushes the shinbone backward to assess PCL looseness.
- MRI: Confirms the tear, grades its severity, and detects injuries to the meniscus or other ligaments.
- X-rays: Rule out fractures or a piece of bone pulled off by the ligament.
Treatment
Treatment depends on the grade of the tear and whether other structures are damaged.
- Initial care: Rest, ice, compression, elevation, and pain relief, often with a brace to support the knee.
- Physical therapy: Most isolated PCL injuries respond well to a rehabilitation program that strengthens the quadriceps to stabilize the joint and restore motion.
- Surgery: Reserved for severe tears, persistent instability, or injuries combined with other ligament damage, using grafts to reconstruct the ligament.
Recovery time varies from weeks for mild sprains to several months after surgery.
Prevention
- Wear seat belts to reduce dashboard injuries in collisions
- Strengthen the thigh and hip muscles that stabilize the knee
- Use proper technique and protective equipment in contact sports
- Warm up before activity and maintain good conditioning
- Address any earlier knee injuries fully before returning to sport
When to See a Doctor
See a doctor if your knee swells, feels unstable, or remains painful after an injury or fall. Seek emergency care after high-energy trauma such as a car crash, or if you cannot bear weight, the knee looks deformed, or you have numbness, coldness, or loss of pulse in the foot, which can indicate associated nerve or blood vessel injury that needs immediate attention.
Frequently Asked Questions
Does a PCL injury need surgery?
Many isolated PCL injuries are treated successfully without surgery using bracing and a quadriceps-strengthening rehabilitation program. Surgery is usually considered for severe tears, ongoing instability, or when other ligaments are also damaged.
How is a PCL injury different from an ACL injury?
The PCL keeps the shinbone from sliding backward, while the ACL keeps it from sliding forward. PCL injuries are less common, often cause milder symptoms, and are more frequently managed without surgery than ACL tears.
What is a dashboard injury?
It refers to the knee striking a car dashboard in a collision, which drives the shinbone backward and can tear the PCL. Wearing a seat belt and using vehicle safety features helps reduce this type of injury.
How long does recovery take?
Mild sprains may improve over a few weeks with rehabilitation, while severe tears or surgical reconstruction can require several months before returning to full activity. Your recovery depends on the severity and any associated injuries.
References
- American Academy of Orthopaedic Surgeons (OrthoInfo). Posterior Cruciate Ligament Injuries.
- Mayo Clinic. PCL injury — Symptoms and causes.
- MedlinePlus, U.S. National Library of Medicine. Knee ligament injuries.
- StatPearls, National Library of Medicine. Posterior Cruciate Ligament Injury.