Posterior Cruciate Ligament Injury, Causes and Symptoms

Posterior cruciate ligaments are important to the function of the knee, which in turn is very important to the function of the lower limbs in general. Injuries to one’s posterior cruciate ligament require a great deal of force, and often happen in conjunction with injuries to nearby structures, including bone, cartilage and other ligaments. The injury is not typically as painful as some other ligament injuries, such as to the anterior cruciate ligament (ACL), which also happen much more frequently. These two ligaments are both responsible for holding the knee together, though, and an injury to either can cause a huge setback in mobility and range of motion.

Although posterior cruciate ligament injuries are not as common or as serious as some other injuries to knee ligaments, they can still be serious enough to cause instability, pain and swelling that hold you back from everyday activities for weeks or months. Injuries to this sturdy band of tissue are subtle and somewhat difficult to diagnose and assess, especially considering the close proximity to the cruciate ligaments connected to the thighbone and shinbone, and the anterior cruciate ligaments that cross the knee along with the posterior cruciate ligament, forming an X. Only medical specialists are qualified to make such a diagnosis.  

Anatomy of the Posterior Cruciate Ligament
There are identical posterior cruciate ligaments at the rear of each knee, which help connect the thighbone and shinbone, as well as keeping the shinbone from overextending in the wrong direction, along with the anterior cruciate ligaments and other cruciate ligaments. The thighbone and shinbone meet at the knee joint, where a kneecap protects this system of ligaments and cartilage holding all the bones together. Collateral ligaments on the sides of the knee and cruciate ligaments inside the knee joint act like a system of ropes for these important bones of the lower limbs.  

  • Cruciate ligaments – The anterior cruciate ligaments cross in front of the posterior cruciate ligaments in the knee, allowing the joint to move back and forth. The posterior are the stronger of the cruciate ligaments, which is why they are not injured as frequently. The entire crossing of ligaments in the knee is as small as a pinky finger in most people.
  • Collateral ligaments – The collateral ligaments are located on either side of each knee, with a lateral collateral ligament on the outside and a medial collateral ligament on the inside. These ligaments are not used as often, but they come in handy when the body must prepare for an abnormal sideways movement.

Types of Posterior Cruciate Ligament Injury
Injuries to any ligaments are actually considered sprains. There are three different grades that are used to distinguish injured ligaments based on severity and symptoms:

  • Grade 1 – Only mild damage from over-extension has occurred, but the joint of the knee is still stable and the ligament is still intact.
  • Grade 2 – This is a slightly more severe injury in which the ligament has been stretched to the point of loosening or partial tearing, but the knee may still be somewhat stable.  
  • Grade 3 – Most injuries in this classification involve a complete tearing of the ligament into two pieces, resulting in extensive instability of the knee joint.

Sprains of the posterior cruciate ligaments are usually Grade 1 or 2, which can potentially heal on their own without serious intervention. With proper care, most people who suffer such ligament tears and partial tears can return to their normal athletic and recreational activities once the healing process is over. 

Causes of Posterior Cruciate Ligament Injury
There are many different possible posterior cruciate ligament injury causes. There is usually a powerful force required to injure this ligament, though, since it is the strongest of a network of ligaments in the knee. These are some of the most common posterior cruciate ligament injury causes: 

  • Blow to the knee
  • Overextension of the ligament from stretching or pulling
  • Misstep leading to a fall

Some common scenarios for this type of injury include car crashes in which the knee hits the dashboard, hyperextension injuries during an awkward twisting motion and falls during sports in which a bent knee bears the brunt of the force. In other cases, however, a simple misstep is enough to do it. 

Symptoms of Posterior Cruciate Ligament Injury
There are also many possible posterior cruciate ligament injury symptoms, and not everyone will necessarily experience all of them or experience them in the same way. The symptoms are often subtle and may appear alongside other injury symptoms, so it’s important to see a doctor right away if the symptoms persist following an injury. These are some of the most common posterior cruciate ligament injury symptoms:

  • Pain immediately following a knee injury
  • Quick and steady swelling
  • Stiffness and limpness in the knee
  • Trouble with walking and other lower-limb movements
  • Unstable feeling in the knee

Fortunately, there are several accurate methods for diagnosing and assessing posterior cruciate ligament injuries, such as the posterior drawer, the sag test and various imaging procedures. It’s also important to check patients for fractures and injuries to the anterior cruciate ligament, bones, collateral ligaments, cartilage and/or meniscus, which commonly happen simultaneously when any of the ligaments have been torn or stretched. Early detection and quick treatment can greatly increase the chances of a full recovery.

Surgery is typically the only option on the table in the case of Grade 3 injuries to posterior cruciate ligaments, in which the ligament has completely torn. In most cases, however, the injury can be treated with simple measures followed by rehabilitation. The majority of patients end their treatment with full use of their knees and related regions of the lower limbs. Without a proper evaluation and skilled medical care, however, this simple injury could easily have long-lasting and detrimental consequences.  

The multidisciplinary team of orthopaedic experts at North Shore-LIJ Orthopaedic Institute's Trauma Services in New York treat Posterior Cruciate Ligaments as well as a broad range of conditions that affect the bones within the body.

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