Posterior cruciate ligament (PCL) injury

Posterior cruciate ligament (PCL) injury

Posterior cruciate ligaments (PCL) are important to the function of the knee. Injuries to one’s PCL 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), that happen much more frequently. These two ligaments are both responsible for holding the knee together, and an injury to either can cause a huge setback in mobility and range of motion.

Although PCL 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 ACL that cross the knee along with the PCL, forming an X. Only medical specialists are qualified to make a PCL injury diagnosis.  

Anatomy of the knee

There are identical PCLs at the rear of each knee, which, along with the ACLs and other cruciate ligaments, help connect the thighbone and shinbone, and keep the shinbone from overextending in the wrong direction. The thighbone and shinbone meet at the knee joint, where a kneecap protects this system of ligaments and cartilage that holds 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. 

  • Cruciate ligaments – The ACLs cross in front of the PCLs 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 (LCL) on the outside and a medial collateral ligament (MCL) 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.

Symptoms

There are also many possible PCL 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 PCL 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

Causes

There are many different possible PCL injury causes. Usually a powerful force is required to injure this ligament, since it is the strongest of a network of ligaments in the knee. These are some of the most common PCL 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. 

Types

Injuries to any ligaments actually are considered sprains. There are three different grades, based on severity and symptoms, which are used to distinguish injured ligaments:

  • 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 PCL are usually Grade 1 or 2, and 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. 

Diagnosis

Fortunately, there are several accurate methods for diagnosing and assessing PCL 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 ACL, 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.

Treatment

Surgery is typically the only option in the case of Grade 3 PCL injuries in which the ligament has completely torn. In most other cases, however, the injury can be treated with simple measures followed by rehabilitation. Most 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 trauma and fracture experts at Northwell Health Orthopaedic Institute treats PCL injuries as well as a broad range of conditions that affect the bones.

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