Posterior Cruciate Ligament Injury

Introduction

Posterior cruciate ligament injury happens far less often than does injury to the knee's better known counterpart, the anterior cruciate ligament (ACL). But just because it's less common doesn't mean that posterior cruciate ligament injury isn't painful.

The posterior cruciate ligament and ACL help hold your knee together, giving it stability. If either ligament is torn, you may experience pain, swelling and loss of mobility. The posterior cruciate ligament is most likely to tear during contact sports such as football or in a car accident. Posterior cruciate ligament injury generally causes less pain, disability and knee instability than ACL tears do, but it can still sideline you for several weeks or longer.

Ligaments are strong bands of tissue that attach one bone to another. The cruciate (KROO-she-ate) ligaments connect the thighbone (femur) to the shinbone (tibia). The anterior and posterior cruciate ligaments form a cross in the center of the knee. They help keep the joint stable and protect the femur from sliding on the tibia. The posterior cruciate ligament, located toward the rear of the knee, prevents the shinbone from moving too far backward.

Although the posterior cruciate ligament is very strong, it may tear or rupture if it's pulled or stretched too far - usually because the shinbone is pushed backward in an accident or sports. In the majority of posterior cruciate ligament injuries, other knee ligaments or structures also are damaged. If the posterior cruciate ligament tears completely from its attachment to the shinbone, it may pull off a piece of the bone with it. This is known as an avulsion fracture.

If you injure your posterior cruciate ligament, you may experience pain and swelling at the back of your knee. Occasionally, this injury can cause a feeling of instability or looseness in the knee. Treatment depends on how severe the injury is and how long you've had it.

Causes

The Knee ligaments - Two of the four ligaments that connect the thighbone (femur) to the shinbone (tibia) are the posterior cruciate ligament (PCL) and the anterior cruciate ligament (ACL). The PCL and ACL crisscross one another as they join these leg bones together.

The PCL can tear if your shinbone is hit hard just below the knee, or if you fall on a bent knee. These injuries are most common during:

Motor vehicle accidents. A so-called dashboard injury occurs when the driver's or passenger's bent knee slams against the dashboard, pushing in the shinbone just below the knee and causing the PCL to tear.

Contact sports. Athletes in sports such as football or soccer may tear their PCL when they fall on a bent knee with their foot pointed down. The shinbone hits the ground first and it moves backward. Being tackled when your knee is bent also can cause this injury.

Other causes include bending or extending your knee past its normal position and getting hit on the side of the knee while your leg is twisted.

When to seek medical advice

Call your doctor if you experience signs and symptoms of a PCL injury or if your knee feels unstable. If you're already being treated for a PCL injury, see your doctor if:

Your knee feels more unstable than it was

The pain and swelling return after subsiding

Your injury doesn't seem to be healing over time

Signs and symptoms

Signs and symptoms of a posterior cruciate ligament (PCL) injury may include:

Mild to moderate pain at the back of the knee

Sudden knee swelling and tenderness (within three hours of the injury)

Pain with kneeling or squatting

A slight limp or difficulty walking

Feeling of instability or looseness in the knee, or the knee gives way during activities

Pain with running, slowing down, or walking up or down stairs or ramps

Most people with a torn PCL don't feel a "pop" - the classic sign of an ACL tear - at the time of the injury. Signs and symptoms may be mild or vague, and you might not even notice anything wrong. Over time, the pain may worsen and your knee may feel more unstable. If other parts of the knee are affected, your signs and symptoms will likely be more severe.

Screening and diagnosis

To diagnose a PCL injury and assess its severity, your doctor will do a physical exam. He or she may also do some tests and procedures to learn the full extent of your injury. The exam may consist of the following:

Medical history. Your doctor will ask about the accident or injury, the problems you're having with your knee, how long you've had symptoms and whether you have a history of knee injuries.

Physical examination of the knee. Your doctor may press on your knee to feel for injury, looseness or fluid in the joint from bleeding. He or she may move your knee, leg or foot in different directions and ask you to stand and walk to see if your knee stays in proper position. Your doctor will compare your injured leg with the healthy one to look for any sagging or abnormal movement in the knee or shinbone.

Posterior drawer test. In this test, you lie on your back with your knee bent. Your doctor gently moves your lower leg backward at the knee. If the leg moves back too far, your PCL is torn.

X-ray. An X-ray picture of the bones and tissues in your knee joint won't show a PCL injury, but it can show damage to bones and cartilage, a sagging shinbone or an avulsion fracture.

Magnetic resonance imaging (MRI). This painless procedure uses magnetic fields to create computer images of the soft tissues of your body. An MRI scan can clearly show a PCL tear and determine if other knee ligaments also are injured.

Arthroscopy. If it's unclear how extensive your knee injury is, your doctor may use a surgical technique called arthroscopy to look inside your knee joint. A small, lighted optic tube is inserted into your knee joint through a small incision. The doctor views images of the inside of the joint on a computer monitor or TV screen.

Joint aspiration. This procedure uses a syringe to remove fluid from the joint. Aspiration may be performed if you have significant swelling of the knee that interferes with the joint's range of motion and your ability to use your knee or leg muscles.

Treatment

What treatment is best depends on the extent of your injury and whether it just happened (acute) or you've had it for a while (chronic). For an isolated PCL tear, with no damage to other parts of the knee joint or shinbone, you probably won't need surgery. Many people with a minor PCL injury can return to their previous level of activity after completing a rehabilitation program, which may take from one to four months.

If you have a bad PCL tear combined with other torn ligaments, cartilage damage or a broken bone, you may need surgery to reconstruct the joint. Surgery may also help if your knee remains unstable after a rehabilitation program. If your doctor recommends surgery, it's best to have it within two to three weeks of your injury. After surgery you'll go through a rehabilitation program. Full recovery may take several months.

Short term: To treat the acute injury:

Rest

Apply ice packs to your knee for 20 to 30 minutes every three to four hours for two to three days or until the pain goes away

Elevate your knee by placing a pillow underneath it

Take pain relievers such as ibuprofen (Advil, Motrin, others) as needed

Wrap an elastic bandage around your knee

Use a splint or walk with crutches if needed

Knee brace or other devices - You may need to avoid putting weight on your injured knee for several weeks. You may wear a knee brace to protect the knee during activity and keep it stable. Using crutches also can decrease strain on your knee.

Rehabilitation

After the swelling in your knee goes down, you'll begin a program of exercises to strengthen your front thigh muscles (quadriceps) and restore your knee's normal range of motion. These exercises may include straight leg raises and isometrics. Gradually you'll add more weight-bearing exercises, such as squats and leg presses, and you'll progress with isolated quadriceps strengthening.

Surgery

PCL reconstruction surgery uses arthroscopic techniques to rebuild the ligament. The surgeon inserts a narrow, flexible instrument (arthroscope) with a light and a small camera at the tip into one or two small incisions. This allows the surgeon to see the inside of the knee joint and make the repairs. The surgeon rebuilds the ligament by using a piece (graft) of tendon, usually from a cadaver, or from a tendon in your leg. If some of the shinbone has been pulled off with the torn ligament, the surgeon places screws in the joint.

Prevention

Unfortunately, most PCL injuries happen during accidents that usually aren't preventable. But these suggestions may help you avoid an injury:

Do strengthening exercises for your upper leg muscles (quadriceps and hamstrings), which protect your knee.

Maintain a good leg-stretching routine.

Use proper techniques when playing sports or exercising.

Self-care

If you experience any of the signs and symptoms of a PCL injury - knee pain, a swollen knee or a feeling that your knee is giving out - see a doctor. Your doctor or physical therapist can recommend exercises to do at home to help strengthen your front thigh muscles and help your knee heal. Return to your prior level of activity gradually.

Complications

If you have a PCL injury, in the short term you may have to limit your physical activity until the swelling goes down, your knee and leg movement is normal, and the pain is gone.

The more extensive your PCL injury, the more likely it is that your knee will feel unstable. It may give out during physical activities, such as running, slowing down, or walking up or down stairs.

If your injury causes episodes of knee instability, the cartilage in your knee can become torn and you may develop arthritis in the joint.

 

Courtesy of Mayo Clinic