How common are injuries to the posterior cruciate ligament?
Injuries to the posterior cruciate ligament are less frequent than those of the anterior cruciate, because it requires a greater force to tear the posterior ligament or pull it from the bone.
Peer-reviewed papersQuote from peer-reviewed paper:
".. .Posterior cruciate ligament (PCL) tears comprise 3% of outpatient knee injuries and 38% of acute traumatic knee hemarthroses. These injuries rarely occur in isolation, and up to 95% of PCL tears occur in combination with other ligament tears...."
Citation: Pache S, Aman ZS, Kennedy M, Nakama GY, Moatshe G, Ziegler C, LaPrade RF. Posterior Cruciate Ligament: Current Concepts Review. Arch Bone Jt Surg. 2018 Jan;6(1):8-18. PMID: 29430489; PMCID: PMC5799606.
What is the usual mechanism of injury of the PCL?
The PCL may become injured when there is a severe backwards blow to the upper tibia when the knee is bent.
The classical is a 'dashboard' injury, such as when a car stops abruptly and the passenger is driven forwards and hits the knee on the dashboard. It may also happen if a person falls suddenly onto a bent knee.
A further mechanism of injury is when a blow drives the knee joint backwards (hyper-extension).
Peer-reviewed papersQuote from peer-reviewed paper:
"....The most prevalent trauma mechanism was traffic accidents, notably with involvement of motorcycles and affecting male individuals....."
Citation: Caldas MTL, Braga GF, Mendes SL, da Silveira JM, Kopke RM. Posterior cruciate ligament injury: characteristics and associations of most frequent injuries. Rev Bras Ortop. 2013 Oct 22;48(5):427-431. doi: 10.1016/j.rboe.2012.09.010. PMID: 31304147; PMCID: PMC6565966.
What are the symptoms of a torn posterior cruciate ligament?
Symptoms of a PCL tear include:
- pain at the time of injury, which is not always severe
- swelling of the knee which again is sometimes tense but not always so
- instability with a limp and feelings of 'giving way'.
Diagnosing a PCL tear
Because this injury is often part of a multi-ligament event, and other structures are damaged at the same time, the PCL tear is quite frequently missed in a routine clinical examination.
The surgeon may needs to do special X-rays to be sure of the diagnosis.
Peer-reviewed papersQuote from peer-reviewed paper:
"....When posterior knee instability is discovered on physical exam, posterior stress radiographs should be performed to objectively quantify posterior knee laxity....Kneeling stress radiography allows for comparison of the magnitude of posterior tibial displacement on the femur between the injured and uninjured knees."
Citation: Pache S, Aman ZS, Kennedy M, Nakama GY, Moatshe G, Ziegler C, LaPrade RF. Posterior Cruciate Ligament: Current Concepts Review. Arch Bone Jt Surg. 2018 Jan;6(1):8-18. PMID: 29430489; PMCID: PMC5799606.
Managing the patient with a torn PCL
There is no clear consensus amongst knee surgeons about how to management patients with a torn PCL, especially if it is part of a multi-ligament injury.
Usually the other injuries will be operated on first, and the patient's stability re-assed.
Peer-reviewed papersQuote from peer-reviewed paper:
In this study the " ....greatest median time between the injury and the surgery (105 days) occurred among patients with PCL + LCL/PLC injuries and the smallest time (8.5 days) among those with PCL injury alone due to bone avulsion. Severe injuries such as those of the PCL + LCL/PLC were operated later on in some cases...."
Citation: Caldas MTL, Braga GF, Mendes SL, da Silveira JM, Kopke RM. Posterior cruciate ligament injury: characteristics and associations of most frequent injuries. Rev Bras Ortop. 2013 Oct 22;48(5):427-431. doi: 10.1016/j.rboe.2012.09.010. PMID: 31304147; PMCID: PMC6565966.