PCL Injuries Explained – Why They’re Often Diagnosed Late

The posterior cruciate ligament (PCL) is one of the key stabilizing ligaments of the knee, yet it remains one of the most misunderstood and frequently overlooked knee injuries. Compared to ACL injuries, PCL injuries are less talked about and often diagnosed much later, sometimes months after the initial trauma. This delay in diagnosis can lead to chronic knee pain, instability, and long-term joint problems if not addressed properly.

Understanding what PCL injuries are, how they occur, and why they are commonly missed can help patients seek timely care and avoid complications. This blog explains PCL injuries in detail and highlights the reasons behind delayed diagnosis.

What Is the PCL and Why Is It Important?

The posterior cruciate ligament is located at the back of the knee and connects the thigh bone (femur) to the shin bone (tibia). Its primary function is to prevent the tibia from moving backward relative to the femur. The PCL works along with the ACL and other ligaments to maintain overall knee stability.

Unlike the ACL, which is stressed during twisting and pivoting movements, the PCL is mainly injured due to direct force. Because of its strong structure and protected position within the knee, the PCL is less frequently injured and often remains partially intact even after trauma.

Common Causes of PCL Injuries

PCL injuries usually occur due to high-impact forces that push the tibia backward. Some of the most common causes include:

• Road traffic accidents, especially when the knee hits the dashboard
• Falls onto a bent knee
• Sports injuries involving direct impact, such as football or rugby
• Sudden hyperflexion of the knee

Because these injuries often occur alongside other trauma, the PCL injury itself may not be immediately recognized.

Symptoms of a PCL Injury

PCL injuries often present with milder symptoms compared to ACL tears, which is one of the main reasons they are diagnosed late. Common symptoms include:

• Mild to moderate knee pain
• Swelling that develops slowly
• Difficulty walking downhill or downstairs
• A feeling of weakness or fatigue in the knee
• Occasional instability, especially during weight-bearing activities

In partial PCL tears, symptoms may improve with rest, giving patients a false sense of recovery. However, underlying instability may still be present.

Why Are PCL Injuries Often Diagnosed Late?

Subtle and Delayed Symptoms

Unlike ACL injuries, which often cause immediate swelling and instability, PCL injuries may cause only mild discomfort initially. Patients may continue daily activities, assuming the injury is minor.

Ability to Walk Despite Injury

Many individuals with PCL injuries can still walk and bear weight on the knee. This reduces the urgency to seek medical attention, delaying proper diagnosis.

Focus on Associated Injuries

PCL injuries often occur along with fractures, meniscus tears, or other ligament injuries. In such cases, attention is directed toward more obvious or painful injuries, while the PCL damage goes unnoticed.

Less Awareness Compared to ACL Injuries

ACL injuries are widely known among athletes and the general population, while PCL injuries receive less attention. This lack of awareness contributes to delayed evaluation and diagnosis.

Challenges in Clinical Examination

Special physical tests are required to diagnose PCL injuries accurately. In the presence of swelling, pain, or muscle guarding, these tests may be difficult to perform or interpret.

How Are PCL Injuries Diagnosed?

Clinical Assessment

Orthopedic specialists use specific tests, such as the posterior drawer test and sag sign, to assess PCL integrity. These tests help identify backward instability of the tibia.

Imaging Studies

MRI is the most reliable imaging tool for diagnosing PCL injuries. It provides clear visualization of ligament damage, along with associated meniscus or cartilage injuries. X-rays may be used to rule out fractures or avulsion injuries.

Types of PCL Injuries

PCL injuries are classified based on severity:

• Grade 1: Partial tear with mild instability
• Grade 2: Partial tear with noticeable looseness
• Grade 3: Complete tear with significant instability

The grade of injury plays a major role in determining the appropriate treatment approach.

Treatment Options for PCL Injuries

Non-Surgical Treatment

Most isolated PCL injuries, especially Grade 1 and Grade 2 tears, can be treated without surgery. Conservative treatment includes:

• Activity modification and rest
• Knee bracing to support healing
• Physiotherapy focused on quadriceps strengthening
• Pain and swelling control

The PCL has a good healing potential, and many patients regain satisfactory knee function with proper rehabilitation.

Surgical Treatment

Surgery is usually recommended for severe PCL injuries, combined ligament injuries, or cases with persistent instability. PCL reconstruction involves replacing the damaged ligament with a graft to restore knee stability.

Post-surgical rehabilitation is crucial and may take 6 to 9 months, depending on the severity of the injury and patient activity goals.

Long-Term Effects of Untreated PCL Injuries

If left untreated, chronic PCL deficiency can lead to abnormal knee mechanics. Over time, this may result in:

• Persistent knee pain
• Difficulty with walking and climbing stairs
• Increased stress on cartilage
• Early onset knee arthritis

Early diagnosis and appropriate management significantly reduce these long-term risks.

Conclusion

PCL injuries are often diagnosed late due to subtle symptoms, lower awareness, and the ability to continue daily activities despite injury. However, delayed diagnosis can have serious long-term consequences for knee health.

Any persistent knee pain, weakness, or instability following trauma should be evaluated by an orthopedic specialist. With timely diagnosis and appropriate treatment, most patients with PCL injuries can achieve good knee function and avoid long-term complications.