Posterior Cruciate Ligament (PCL) Injury

A PCL injury can happen on its own, which is called an isolated injury. It often happens together with damage to other ligaments, such as the posterolateral corner on the outer back of the knee. In a registry of 1,287 people who had PCL surgery in Scandinavia, about 6 in 10 had at least one other ligament injured.^[4] When several ligaments are torn, it is called a multiligament injury.

How are PCL injuries graded?

Doctors grade a PCL injury by how far the shin bone moves backwards compared with your other knee:

• Grade 1: The ligament is stretched, but the knee stays stable.
• Grade 2: The ligament is partly torn, and the knee is looser.
• Grade 3: The ligament is completely torn, and the shin bone sags back further.

Sometimes the ligament pulls off a small piece of bone where it attaches to the shin bone. This is called an avulsion fracture.

What causes a PCL injury?

The PCL tears when a force pushes the top of your shin bone backwards. Common causes are:

• A dashboard injury, when the knee hits the dashboard in a car crash
• Falling onto a bent knee with the foot pointed, for example in football
• A direct blow to the front of the shin in a contact sport
• The knee bending backwards too far (hyperextension) or twisting, which often damages other ligaments as well

In a study of 494 people with PCL injuries, traffic accidents (45%) and sport (40%) were the main causes. Dashboard injuries (35%) and falls on a bent knee (24%) were the most common ways the ligament was torn.^[1]

What are the symptoms of a PCL injury?

Symptoms are often milder than after an ACL tear, so a PCL injury can be missed at first. You may notice:

• Pain at the back of the knee
• Swelling over the first few hours or days
• Stiffness and difficulty bending the knee fully
• A limp
• The knee feeling loose or unsteady, especially on stairs or slopes
• Later on, aching at the front of the knee or behind the kneecap

When should you see a doctor?

See your GP or physiotherapist after any knee injury that causes swelling, or if your knee has not settled after a week or two. Seek urgent medical care if:

• You cannot put weight on your leg
• Your knee looks out of shape or felt as if it came out of joint
• Your foot is cold, pale, numb or weak. Severe ligament injuries can damage the nerves and blood vessels behind the knee.
• Your knee keeps giving way

How is a PCL injury diagnosed?

Diagnosis starts with how the injury happened and an examination. With your knee bent, the doctor checks whether the top of the shin bone sags back compared with your other knee. They then gently push the shin bone backwards to feel how far it moves (the posterior drawer test).

X-rays look for a fracture, including an avulsion fracture. An MRI scan shows the ligament itself and any damage to other ligaments, the menisci (the cartilage cushions in the knee) and the joint surface. MRI is very accurate for a recent tear. It can miss an older tear, because a ligament that has healed in a stretched position can look normal on the scan.^[5] Dr Vishal Pai may also arrange stress X-rays, taken while the shin bone is pushed backwards, to measure how loose the knee is.

How is a PCL injury treated without surgery?

Most isolated PCL injuries are treated without surgery, and this usually includes complete (grade 3) tears. A torn PCL can often heal, especially if the shin bone is held in the right position while it does. In a small study that repeated MRI scans over a year, 12 of 18 torn PCLs had healed back into one piece. The ones that did not heal were the most severe tears, with damage at the outer back of the knee as well.^[6]

PCL brace

A PCL brace has a pad or strap behind the calf that pushes the top of the shin bone forward. This holds the ligament at the right length while it heals. A grade 1 sprain does not need a brace. For grade 2 and 3 tears, Dr Vishal Pai uses a PCL brace for 12 weeks. Wearing the brace as advised is an important part of the treatment.

Physiotherapy and quadriceps strengthening

Physiotherapy is the main treatment. The quadriceps is the large muscle at the front of your thigh. When it contracts, it pulls the shin bone forward, so a strong quadriceps helps make up for a loose PCL. In a study of 25 athletes followed for about 6 years, those who were satisfied with their knee had quadriceps at least as strong as on their other leg. Those who were not satisfied all had weaker quadriceps.^[7]

Early exercises aim to settle the swelling and get the knee moving. Hamstring exercises pull the shin bone backwards, so they are usually limited at first. Strength, balance and sport-specific training follow.

Pain relief and getting back to activity

Ice, raising your leg, simple pain relief and crutches for the first few days can help. Your return to running and sport is gradual. It is guided by your strength and how your knee feels, rather than a fixed date.

When is surgery considered?

Surgery is considered when the PCL is torn together with other ligaments, when a piece of bone has pulled off and moved out of place, or when a complete tear still leaves your knee unstable after a good course of bracing and physiotherapy. Multiligament injuries usually need surgery.

The usual operation is a PCL reconstruction, which replaces the torn ligament with a graft. Dr Vishal Pai uses either your own hamstring tendons or donor tissue, and you wear a dynamic PCL brace for 12 weeks afterwards.

What is the outlook for a PCL injury?

Many people recover well without surgery. In a group of 46 athletes with grade 2 or 3 isolated tears treated with a brace and rehabilitation, the average return to full competitive sport was about 16 weeks (range 10 to 40 weeks). Two years after the injury, 9 in 10 were playing at the same or a higher level. By 5 years, this was about 7 in 10.^[2]

In a long-term study of 68 people treated without surgery and followed for an average of 14 to 17 years, most stayed active, with good thigh strength and full movement. Moderate or severe arthritis was seen in 11%.^[3]

A PCL injury does raise the long-term risk of arthritis. In a population study, people with an isolated PCL tear were about six times more likely than people without one to develop knee arthritis that caused symptoms over 12 years. The risk was higher for those injured at an older age.^[8] Keeping your quadriceps strong is one of the most useful things you can do for your knee.^[7]

References

Show all 8 referencesHide references

1. Schulz MS et al. 2003. Epidemiology of posterior cruciate ligament injuries. Archives of Orthopaedic and Trauma Surgery.
2. Agolley D et al. 2017. Successful return to sports in athletes following non-operative management of acute isolated posterior cruciate ligament injuries: medium-term follow-up. The Bone & Joint Journal.
3. Shelbourne KD et al. 2013. Minimum 10-year follow-up of patients after an acute, isolated posterior cruciate ligament injury treated nonoperatively. The American Journal of Sports Medicine.
4. Owesen C et al. 2015. Epidemiology of surgically treated posterior cruciate ligament injuries in Scandinavia. Knee Surgery, Sports Traumatology, Arthroscopy.
5. DePhillipo NN et al. 2018. Posterior tibial translation measurements on magnetic resonance imaging improve diagnostic sensitivity for chronic posterior cruciate ligament injuries and graft tears. The American Journal of Sports Medicine.
6. Mariani PP et al. 2005. Evaluation of posterior cruciate ligament healing: a study using magnetic resonance imaging and stress radiography. Arthroscopy.
7. Parolie JM et al. 1986. Long-term results of nonoperative treatment of isolated posterior cruciate ligament injuries in the athlete. The American Journal of Sports Medicine.
8. Sanders TL et al. 2017. Incidence and long-term follow-up of isolated posterior cruciate ligament tears. Knee Surgery, Sports Traumatology, Arthroscopy.