What is Posterior Cruciate Ligament Knee Injuries?
The Posterior Cruciate Ligament (PCL) is one of the four critical ropes-like structures in the knee. Its job is to keep the shin bone (tibia) stable on the thigh bone (femur). It starts from the inside front part of the rounded end of the thigh bone (medial femoral condyle) and attaches to the back part of the flat top area of the shin bone (tibial plateau). Its main role is to stop the shin bone from moving too far backwards on the thigh bone. It also helps to withstand other forms of stress on the knee, such as sidewards motion (varus and valgus) and twisting (external rotation). It’s more substantial and stronger, almost twice as much, as the anterior cruciate ligament (ACL), another important knee ligament, which makes it less likely to get injured.
What Causes Posterior Cruciate Ligament Knee Injuries?
Damage to the PCL, or posterior cruciate ligament that is located in your knee, happens when a forceful push is applied to the top part of your shinbone while the knee is bent. This type of injury often occurs during car accidents when the knee is forcefully driven into the car’s dashboard. You can also hurt your PCL if you fall onto your knee when it’s bent.
These injuries often happen during sports like football, skiing, soccer, and baseball. In rare cases, a PCL injury can happen when the knee is forcefully twisted and overextended.
Risk Factors and Frequency for Posterior Cruciate Ligament Knee Injuries
A study in 2003 found that the average age when PCL (Posterior Cruciate Ligament) injuries occur is 27 years old. There are several common causes, with the majority of these injuries resulting from car accidents and sports incidents. Furthermore, motorcycle accidents and soccer-related injuries have been identified as the two most common specific causes. The most prevalent types of injuries are dashboard injuries and falling on a bent knee with the foot bent downwards. Males are twice as likely to sustain a PCL injury compared to females.
- The average age for PCL injuries is 27.
- The two primary causes are car accidents (45%) and athletic injuries (40%).
- Motorcycle accidents (28%) and soccer-related injuries (25%) are the specific leading causes.
- Dashboard injuries (35%) and falls on a flexed knee with the foot bent downwards (24%) are the most common types of injuries.
- The ratio of males to females with PCL injuries is 2:1.
Signs and Symptoms of Posterior Cruciate Ligament Knee Injuries
When patients have severe pain, swelling, and instability at the back of their knee, they might have a posterior cruciate ligament (PCL) tear. This type of injury can be caused by trauma such as a fall or a car accident. Some patients might notice a ‘pop’ sound at the time of the injury, however this is not always the case.
The doctor will conduct an examination, checking the patient’s overall leg alignment and how they walk. They will also evaluate if there is any disruption to the blood supply below the injury site. It is important to act immediately if there is any indication of weak blood flow to the lower leg/foot.
On inspection, patients with a PCL tear may show:
- Mild to moderate joint swelling, which is usually less than that caused by an ACL tear.
- A limp or altered gait, favoring the affected knee.
- Challenges with walking up and down stairs or on an incline.
- A positive sag test, indicating the tibia suffers a downward sag compared to the other knee.
The strength and mobility of the affected knee are also tested:
- Strength may be normal, but due to the pain caused, there might be some weakness when extending or flexing the knee.
- There could be a limitation in passive range of motion, reducing knee flexion by 10 to 20 degrees. This could be further decreased with other injuries such as meniscal, muscular, or ligament injuries.
Additional special tests include the posterior drawer test, quadriceps active test, dial test, and varus/valgus stress test to exactly determine the nature of the injury and the extent to which PCL or other ligaments are involved.
Testing for Posterior Cruciate Ligament Knee Injuries
If a doctor suspects an injury to your posterior cruciate ligament (PCL, one of the four main ligaments in the knee), they’ll initially order simple X-ray images. They will ask you to stand and take different angled X-rays of the knee, including the other knee for comparison. X-rays can help identify any related issues, such as fractures or joint inflammation. In some images, your doctor may notice a “sag” or droop in your knee, which could be a sign of an injured PCL.
However, an MRI imaging test (using strong magnetic fields to create a detailed image of your knee) is usually regarded as the best method for diagnosing PCL injuries. This is because MRI scans are very accurate, with an accuracy range of 96% to 100%. Not only can an MRI confirm an injury to your PCL, but it can also identify any other damage in your knee, like to your meniscal (a type of cartilage in your knee), other ligaments, or your joint capsule (the structure that encloses the joint).
On an MRI, a PCL injury might appear as an interruption in the ligament fibers or an unusually bright spot within the ligament tissue. This suggests a recent PCL injury. If your PCL injury is older, your MRI might show that the lower bone in your leg (the tibia) has moved backward compared to normal. If this backward movement is less than 8 mm, it might be possible for your PCL to heal on its own.
When doctors look at these imaging tests, they assess PCL injuries on a scale that ranges from grade I to grade III:
- Grade I (partial tear): Your lower leg moves backward slightly (1-5mm). The tibia still sits in front of the femoral condyles (the rounded ends of the thigh bone).
- Grade II (complete isolated tear): Your tibia moves backward slightly more (6-10mm). In this case, the PCL is completely torn but there are no other injuries. The front of the tibia sits flush with the femoral condyles.
- Grade III (complete PCL with combined capsular and/or ligamentous injury): Your tibia moves backward quite far (more than 10mm). This might indicate that there is also damage to the joint capsule or other ligaments in your knee.
Treatment Options for Posterior Cruciate Ligament Knee Injuries
When it comes to managing an injury to your posterior cruciate ligament (PCL), a type of knee injury, doctors look at several key factors. These include whether the injury is new or old, and whether the PCL was the only part of the knee that was injured. In the past, PCL injuries were typically treated without surgery, regardless of the severity of the injury. This was partly because the surgical procedures available at the time often yielded inconsistent results. However, advances in surgical technology and techniques have made PCL reconstruction a more reliable option, although the long-term results of this procedure are not yet clear.
Treatments without surgery are usually recommended for:
- Recent mild to moderate injuries with a tibial translation (a type of knee displacement) between 8 mm and 12 mm.
- Those with severe injuries who only have mild symptoms or don’t do high-demand activities.
In these cases, the PCL can often heal itself. The first step in treating the injury includes rest, applying ice, using compression bandages, and elevating the injured area, typically referred to as the RICE method. First, patients may be given a knee brace which can help control pain, reduce knee displacement, and manage an isolated PCL injury. Crutches can also be used until the strength is restored in the quadriceps (the muscle group at the front of your thigh). Rehabilitation is important; it focuses on strengthening the muscles that extend the knee. Usually, patients can return to their activities in 2 to 4 weeks. Severe injuries can be treated with a knee immobilizer for one month before moving into the rehabilitation phase of recovery.
Surgery may be recommended in cases of:
- New injuries with a tibial translation more than 12 mm, repairable meniscal tears, knee dislocation, bone avulsions, and combined ligament injuries.
- Old injuries with a tibial translation more than 8 mm, symptoms with deceleration or descending inclines, instability and combined ligament injuries.
Surgical procedures often used for PCL reconstruction include techniques such as single bundle and double bundle, with the choice between using your own tissue vs. someone else’s (autograft vs. allograft). These techniques are mostly performed using an arthroscopy, which involves making small incisions in the knee and using a special camera to guide the procedure.
The single-bundle technique is the traditional way of PCL reconstruction. The double-bundle technique aims to restore the normal motion of the knee. It involves creating one tunnel in the tibia (shin bone) and two in the femur (thigh bone).
There are two main ways to secure the tissue graft used in the reconstruction: the transtibial tunnel and the tibial-inlay. The transtibial method has been known to cause graft failure due to a sharp angle, called the “killer turn”, at the exit of the tunnel created in the tibia. The tibial inlay method secures the graft with an anchor or screw, with its own risk of being too close to a major artery.
High Tibial Osteotomy (HTO) is another surgical option. It’s generally only used in cases where the PCL injury is chronic, and the knee is deviating outward. It aims to delay the progression of secondary osteoarthritis, which is a type of joint disease that results from breakdown and eventual loss of the cartilage of one or more joints.
What else can Posterior Cruciate Ligament Knee Injuries be?
If you’re having knee or ankle issues, a doctor might consider several potential problems. The issue might be:
- An injury to the anterior cruciate ligament (this is in your knee)
- A lateral collateral knee ligament injury (another type of knee injury)
- A medial collateral knee ligament injury (yet another type of knee injury)
- Injuries to the meniscus (this is a specific type of cartilage in your knee)
- An injury to the talofibular ligament (this is in your ankle)
Possible Complications When Diagnosed with Posterior Cruciate Ligament Knee Injuries
Intraoperative and postoperative complications when undergoing surgery for the Posterior Cruciate Ligament (PCL) include the following:
- Injury to the neurovascular structures, such as the Popliteal artery
- Bone fractures
- Continuing instability of the knee joint
- Progression of osteoarthritis, specifically in the kneecap (patellofemoral) and the inner knee (medial tibiofemoral)
- Osteonecrosis, which is the death of bone tissue due to lack of blood supply
- Stiffness in the knee
- Failure of associated ligament reconstructions or repairs to the meniscus, which is the cartilage in the knee
- Need for a repeat PCL surgery
Recovery from Posterior Cruciate Ligament Knee Injuries
Rehabilitation plays a crucial role in ensuring good recovery after an injury or surgery to the posterior cruciate ligament (PCL), a ligament in the knee. Different rehabilitation approaches exist, but there are some key principles that should guide any program. These include: gradually increasing weight-bearing and range of motion exercises, avoiding exercises that could lead to sliding of the lower leg bone backward early in recovery, and focusing on strengthening the quadriceps, a muscle group on the front of your thigh, from the get-go.
A 5-phase post-surgery recovery program was suggested by a researcher named Pierce. After the surgery, patients use a special kind of knee brace for three days and then switch to another type of brace. It’s recommended that this second brace is worn all the time for 24 weeks after surgery.
In the first phase (0 to 6 weeks):
* For the first two weeks, patients perform a range of motion exercises in a lying down position.
* From the third to the sixth week, patients continue these exercises as much as they can tolerate.
In the second phase (7 to 12 weeks):
* Patients start to gradually put more weight on the leg as much as they can manage.
* We ensure the knee bends less than 70º during weight-bearing exercises.
In the third phase (13 to 18 weeks):
* The knee can bend more than 70º during exercises after the 16th week.
* Patients continue wearing the brace.
In the fourth phase (19 to 24 weeks):
* Patients slowly start doing drills related to their specific sports.
In the last phase (25 to 36 weeks):
* If the graft is healed sufficiently, as seen in the 6 months post-surgery stress x-rays, patients can start to stop using the brace.
* Patients start a jogging progression in a straight line.
* The final goal is to slowly start practicing agility exercises in different directions, aiming to return to pre-surgery activities.
