PCL Knee Injuries
The posterior cruciate ligament (PCL) is the strongest ligament of the knee. Typically, it isn’t as well known as the other cruciate ligament in the knee, the anterior cruciate ligament (ACL). This could be because it is less commonly injured than the ACL.
Injured ligaments are classified as sprains and are graded on a severity scale:
- Grade 1: Ligament has been slightly stretched, but is still able to help keep the knee joint stable.
- Grade 2: The ligament has been stretched to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
- Grade 3: Most commonly referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the knee joint is unstable.
Anatomy of the Knee
Ligaments are tough bands of tissue that connect the ends of bones together. The PCL is located near the back of the knee joint. It attaches to the back of the femur (thighbone) and the back of the tibia (shinbone) behind the ACL.
The PCL is the primary stabilizer of how far backward the tibia moves under the femur. This motion is called posterior translation of the tibia. If the tibia moves too far back, the PCL can tear (rupture).
The PCL along with the posterolateral corner ligaments also prevents rotatory movements of the knee (also called rotational movements).
The PCL is made of two thick bands of tissue bundled together. One part of the ligament tightens when the knee is bent; the other part tightens as the knee straightens. This is why the PCL is sometimes injured along with the ACL when the knee is forced to straighten too far, or hyperextend.
Both bundles of the PCL not only change length with knee flexion and extension, but they also change their orientation (direction of the fibers) from front-to-back and side-to-side. This function allows the ligament to keep the tibia from sliding too far back or slipping from side-to-side.
You can learn more about the anatomy of the knee by downloading our educational document A Patient’s Guide to Knee Anatomy.
How PCL Knee Injuries Occur
Typically, a posterior cruciate ligament injury requires a powerful force.
The most common way for the PCL to be injured is from a direct blow to the front of the knee while the knee is bent, such as a fall onto a bent knee while playing sports or hitting a bent knee on the dashboard during a car accident.
Other parts of the knee may be injured when the knee is violently injured. In most cases, however, other ligaments are usually injured or torn before the PCL.
Symptoms of PCL Knee Injuries
The symptoms following a tear of the PCL can vary. Common symptoms may include:
- Feeling of stiffness and some swelling in the back of the knee
- Instability, where the knee feels as though it will give out from under you
- Difficulty walking
The pain and swelling from the initial injury will usually be gone after 2 to 4 weeks, but the knee may still feel unstable. The symptom of instability or the inability to trust the knee for support are what require treatment. Also, important in the decision about treatment, is the growing realization by orthopedic surgeons that long-term instability leads to early arthritis of the knee.
You can learn more about arthritis of the knee by downloading our educational document A Patient’s Guide to Osteoarthritis of the Knee.
Diagnosing PCL Knee Injuries
Our team of orthopedic surgeons will start with a thorough history and physical exam of your injured knee. During the physical examination, special stress tests are performed on the knee. Three of the most commonly used tests include:
- Posterior Lachman test
- Posterior sag test
- Posterior drawer test
Tests are also done to see if other knee ligaments or joint cartilage have been injured as well. Typically, we will obtain x-rays of your knee to rule out a fracture. In most cases, special stress x-rays are obtained to help determine the extent of the injury to the PCL.
Because ligaments and tendons do not show up on x-rays, an MRI scan may also be needed in order to view the PCL and other soft tissues of the knee more clearly.
In some cases, arthroscopy may be used to help determine additional injuries to ligaments, menisci and cartilage in a PCL-injured knee. Arthroscopy is a type of operation where a small fiber-optic camera is placed into the knee joint, allowing the surgeon to look at the structures inside the joint directly. Arthroscopy is also used when repairing a torn PCL.
If you are diagnosed with an PCL injury, your SROSM physician will talk with you about the best course of treatment for you.
You can learn more about PCL injuries by downloading our educational publication A Patient’s Guide to Posterior Cruciate Ligament Injuries.