What Causes a Posterior Cruciate Ligament Injury?

Posterior cruciate ligament injuries occur less frequently than anterior cruciate ligament injuries, however, they shouldn't be underestimated. Especially when they're associated with an automobile accident.
What Causes a Posterior Cruciate Ligament Injury?

Last update: 22 June, 2021

The posterior cruciate ligament is the strongest ligament in the knee joint. It’s referred to as posterior because it runs across the back of the knee. It connects the tibia to the femur and, together with the anterior cruciate ligament, maintains the stability of the area. Both cross inside and form an X in the center of the joint. But what if you get a posterior cruciate ligament injury?

The injuries of the posterior cruciate ligament happen less frequently than those of the anterior cruciate ligament. The latter is considered to be the most vulnerable.

There’s usually less pain and instability, but the disability may last for several weeks or months. Here’s more information.

Symptoms of posterior cruciate ligament injury

Most people with a posterior cruciate ligament injury feel pain right away and then have swelling. The sensation they describe is that the knee feels weak and loose, as if it won’t support their weight.

The pain may be severe and appear along with difficulty walking, so there may be limping. Although it’s also important to note that the symptoms of a posterior cruciate ligament injury can be so mild that you may not even notice them.

Eventually, pain begins to appear or the knee begins to feel unstable. It’s at this point that the person seeks medical attention and discovers that they experienced an injury some time ago.

Degrees of injury

The classification of posterior cruciate ligament injuries is according to the size of the displacement of the bones in the knee joint. The degrees of injury are divided as follows:

  • First degree or partial: Involves a backward displacement of the shin bone of 1 to 5 millimeters.
  • Second degree or complete: In this case, the backward displacement of the shinbone is 6 to 10 millimeters.
  • Third degree: The backward displacement of the shinbone is greater than 10 millimeters of translation. It indicates that there’s a lesion of the posterior cruciate ligament and of the anterior cruciate ligament as well.
A man holding onto his knee.
Pain and swelling are the most obvious signs of posterior cruciate ligament injury.

Main causes

Many knee injuries occur while playing sports. However, posterior cruciate ligament injuries are most often the result of a motor vehicle accident. It occurs when a person receives a blow just below the knee or when their own weight falls on the flexed joint.

Other frequent mechanisms of injury of this ligament are the following:

  • When the knee is impacted backward very quickly.
  • The shinbone hits very hard against something firm, such as the dashboard of the car.
  • The knee twists or overextends suddenly.

What does the diagnosis of a posterior cruciate ligament injury involve?

To perform the initial assessment, the doctor will ask how the injury took place. Next, they’ll need to look at both knees to determine if one looks different from the other.

If there is, indeed, a posterior cruciate ligament injury, the knee will tilt backward in a non-anatomical way when you straighten your leg.

Another maneuver is to put pressure on the shin with the knee bent at a 90-degree angle. If the tibia moves more than normal, it’s very likely that the posterior cruciate ligament has been injured.

When the case requires it, the practitioner may order one or more of the following imaging studies:

  • X-rays: Although it’s not possible to detect if there’s damage to the ligament, it reveals fractures of the bones involved.
  • Magnetic resonance imaging: With this technique, it’s possible to observe if there’s a tear of the posterior cruciate ligament and if the other soft parts also have lesions.
  • Arthroscopy: With this study, specialists can observe the interior of the knee. They insert a small video camera into the joint and analyze the internal structures.

Available treatments for a posterior cruciate ligament injury

Treatment depends on the extent of the injury and the time that has elapsed since it happened. It can be non-surgical or surgical.

Non-surgical

In the case of a minor injury, it’s possible to initiate treatment by physical means. For example, applying cold therapy and raising the knee while sitting. An elastic bandage is also used to prevent swelling and limit movement.

Over-the-counter pain relievers, such as ibuprofen or naproxen, help to relieve the pain. These medications also help reduce swelling.

Surgical

Most people don’t need surgery to repair a posterior cruciate ligament injury. Athletes most often do require it.

Repairing a posterior cruciate ligament doesn’t involve reattaching it. This union doesn’t strengthen well and can tear again.

For this reason, the doctor removes the injured ligament and replaces it with new tissue. This procedure is performed arthroscopically for faster recovery. It also results in less scarring.

Knee surgery.
Arthroscopy is a minimal intervention that reduces risks and prevents the need for open surgery.

Recovery and future projection

Physical therapy through specific exercises can strengthen the leg muscles. In this way, the intention is to restore full range of motion to the knee joint.

After surgery, physical therapy should begin 1 to 4 weeks later. The duration may require a period of 6 months for complete improvement.

Injuries involving more ligaments tend to have a slower recovery. Most patients improve satisfactorily with time. Although it’s a slow process, physical therapy is very important in order to be able to perform all daily activities again.

Posterior cruciate ligament injury: A treatment plan

Once a posterior cruciate ligament injury has been diagnosed, a treatment plan is essential. The time involved in recovery will depend on the severity and the structures involved.

Some people may benefit from using crutches for a few days after surgery. An orthopedic brace may also be recommended in order to prevent the bending of the knee.

Complete recovery from posterior cruciate ligament reconstruction takes up to a year. It’s very important to emphasize that most people will be able to return to their pre-injury activities.

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