Posterior Cruciate Ligament Injury

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Original Editors - Sigrid Bortels as part of the Vrije Universiteit Brussel's Evidence-based Practice project

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Definition/Description

A posterior cruciate ligament (PCL) injury can appear in different forms and degrees. They are less common than anterior cruciate ligament (ACL) injuries because the PCL is much broader and much stronger. A PCL injury can be isolated or combined with other ligamentous injuries. The severity of the injury determines the treatment protocol. The severity can range from a stretch of the ligament to a total rupture of the ligament in the transverse direction. A rupture varies in degrees of disability, from no impairment to severe impairment. [1] In a first degree PCL-injury the damage is limited, there are only microscopic tears. In a second degree there is a partial tear of the ligament and the patient will experience a small feeling of instability. In a third degree the ligament is completely torn. [10] In part 5, Characteristics, these criteria are discussed.

Clinically Relevant Anatomy

The posterior cruciate ligament (PCL) is found in the knee joint and runs from the internal surface of the medial femoral condyle [2] to the centre of the posterior aspect of the tibia plateau (area intercondylaris posterior), 1 cm below the articular surface of the tibia [3]. The PCL and the anterior cruciate ligament (ACL) run in opposite direction to form an ‘X’.
The PCL is twice as thick as the ACL, which means that it is much stronger. Therefore PCL injuries are less common than ACL injuries.

A PCL consists of two inseparable bundles: the wide [3] anterolateral bundle (AL) and the smaller posteromedial (PM) bundle.
The AL bundle is most tight in midflexion of the knee and inward rotation, while the PM bundle is most tight in knee extension and deep flexion. [2][3]

The orientation of the fibers varies between bundles. The AL bundle is more horizontally orientated in extension and becomes more vertical as the knee is flexed beyond 30°. The PM bundle is vertically orientated in knee extension and becomes more horizontal through a similar range of motion. 

The PCL is the major stabilizing ligament of the knee. Its primary function is resisting the posterior displacement of the tibia in relation to the femur. Its secondary function is preventing hyperextension and limiting internal rotation, adduction (varus rotation) and abduction (valgus rotation). [3]

Epidemiology /Etiology

The most frequent mechanism of PCL injury is a direct blow to the anterior aspect of the proximal tibia when the knee is flexed, resulting in posterior translation of the tibia platform. Hyperextension and rotational or varus/valgus stress mechanisms may also be responsible for PCL tears. [1][7]

This occurs mostly during sports, such as football, soccer and skiing. In the study of Fowler and Messieh[8], isolated PCL injuries were commonly reported in athletes and hyperflexion was the most frequent mechanism of injury. [7]

A PCL injury can also result from a car accident in which a posterior force is applied to the tibia when the flexed knee hits the dashboard ('Dashboard injury'). This can be combined with posterolateral ligament injuries if the anteromedial aspect of the knee strikes the dashboard with a varus force applied.[9] Also a bad landing from a jump, a simple misstep or fast changes of direction can result in a PCL injury. [6][7]

The study of Peterson et al. says the incidence of PCL injury in the United States is unknown. They did, however, find a 2% incidence of isolated, asymptomatic and unknown PCL injuries in National Football League predraft physical examinations. An incidence of 3,5-20% was reported for operated, isolated and combined PCL injuries. [1]

Characteristics/Clinical Presentation

Characteristics 

- Grade 1 Sprains. The ligament is slightly stretched. (AL and/or PM bundle)
- Grade 2 Sprains. The ligament is stretched to the point were it becomes loose. (AL and/or PM bundle)
This is called a partial tear.
- Grade 3 Sprains. This is a complete tear of the ligament.
The ligament has been split into two pieces, and the knee joint is unstable. 

Clinical Presentation

- Movement restrictions and pain
- A weak feeling in the knee
- Swelling
- Knee joint instability
- Difficulty walking
 

Differential Treatments

Grade 1 sprains. Conservative treatment : it is a non-operative treatment. An example of a conservative treatment is physical therapy. This is the most important treatment for physiotherapists and is explained further bellow.

Grade 2 sprains. The treatment options are somewhat controversial, but the following guidelines can be considered as general guidelines:
- An isolated acute PCL tear with less than 10 mm of posterior laxity at 90 degrees of flexion will probably be treated with physical therapy.
- An acute PCL tear that causes more than 10 to 15 mm posterior laxity or more than one ligament injury, will be treated with surgery in order to repair or reconstruct the PCL.
- Sometimes, a portion of bone is pulled off with the torn ligament. If the fragment is large enough, the bone is usually reattached. If the fragment is too small, it is discarded and the PCL is repaired or reconstructed.
- All chronic PCL injuries are initially treated with an aggressive quadriceps rehabilitation program. But if the aggressive rehabilitation program fails, if there is more than 10 to 15 mm posterior laxity in the knee, or if degenerative changes in the knee joint can be seen on x-rays, surgery may be required. An operation to treat a long-term PCL injury does not make the knee normal, but it may decrease its laxity. 

-> These are the general guidelines, but after reading some articles about the conservative treatment of grade 2 sprains, it is clear that the results are controversial.
Some experiments are rather positive about conservative treatment, and conclude that almost all patients can resume their normal sport activities after treatment, without further problems.
But there are also other studies that are rather negative. One study concluded that significant symptoms and degenerative changes increase with increasing interval from injury. But can early reconstruction prevent degenerative changes? According to another article, this still remains uncertain.
Another study concludes that the posterior instability of the PCL injured patients showed little improvement when compared with the initial status before the treatment and that residual laxity still remained.
It is probably necessary to realize more studies in order to know what treatment is best for grade 2 injuries.

Grade 3 sprains. Use of an operative treatment. This means repairing the ligament by reattaching the torn fibres to each other.
If not enough fibres remain to repair the PCL or if the tissue has degenerated beyond repair, the PCL can be reconstructed. The ligament will be replaced with tissue from another part of the body or from a donor. Part of the patellar tendon (tissue that connects the muscle to the patella) or hamstrings can be used in the reconstruction. 
 

Diagnostic Procedures

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Outcome Measures

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Examination

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Medical Management

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Physical Therapy Management

1. RICE- method: Rest, Ice, Compression, Elevation → helps to speed the recovery.

2. Physical therapy: it is a careful rehabilitation program, with specific exercises to stretch and strengthen the leg muscles and to restore function in the knee. Strengthening the quadriceps is the key factor in a successful recovery, because the quadriceps can take the place of the PCL to a certain extent, helping to prevent the femur from moving too far forward over the tibia.
Some therapists recommend the use of a knee brace to support the knee during movement or when the patient is engaged in athletic activity. The use of a brace has not yet been shown effective during exercises.

These are some typically exercises for a PCL injury.

• "Closed chain" exercises (minisquats, gentle stretching, leg press, bicycling, stair-stepper exercises).- Proprioceptive exercises such as balance-board therapy, mini-trampoline balancing.
• Full range of motion should be achieved 4-6 weeks after injury.
• Functional training (for sporters), beginning with forward and backward running and progressing to lateral movements, and sport-specific activities.

Key Research

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Resources

1. http://www.wheelessonline.com/ortho/anatomy_of_the_posterior_cruciate_ligament
2. http://www.arthroscopy.com/sp05001.htm
3.Gerard B. Rondhuis (1196). Knierevalidatie, Elsevier/De Tijdstroom
4.http://orthoinfo.aaos.org/topic.cfm?topic=a00420
5. http://www.hughston.com/hha/a.pcl.htm
6. R. Timothy, M.D. Stapleton (1996). The posterior cruciate ligament, Hughston Health Alert, 8, nr. 1, 2-3.
7. E. Brown David, D. Neumann randall (2004). Orthopedic secrets, 3, Philadelphia, Pennsylvania 
8. http://www.healthcentral.com/encyclopedia/408/264.html

Clinical Bottom Line

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Recent Related Research (from Pubmed)

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