The posterior cruciate ligament (PCL) is a strong and thick ligament in the middle of the joint working as a restraint to posterior drawer of the tibia. It may be torn in high energy accidents as road accidents (car or motorbike) and sometimes in contact sports accidents.
In an acute setting, the knee is swollen (haemarthrosis) and a skin lesion is typically seen on the front part of the tibia, where the impact producing a violent tibial posterior drawer occured. Clinically, the posterior drawer of the tibia is seen when the patients lies on a bed with knees flexed at 90°, muscles relaxed: it is called the “posterior sag” sign. One can feel the posterior drawer and the posterior laxity, even more if the posterolateral or posteromedial corners have been damaged too.
The patient should go in an emergency unit to get Xrays of the knee to rule out a fracture, and to get a clinical examination. If a posterior laxity is felt, an MRI is necessary to confirm the PCL tear and to look for associated lesions are meniscal tear, collateral ligament tear (MCL or LCL), bone bruises. A knee specialist should be consulted to get a precise clinical examination and discuss the best treatment. The choice between a conservative versus a surgical treatment relies on many criteria: the severity of the lesions in the knee, the patient usual sports activity and his expectations, the patient professional activity, age, and symptoms.
A conservative treatment is recommended for interstitial tear of the PCL because this ligament has a good potential to heal, because it is well vascularised. The goal of the conservative treatment is to get the range of motion back, avoiding a posterior drawer in order to let the PCL heal without tension. To to so, the rehabilitation protocol is done prone on the treatment table, and the knee is locked in an extension brace for 6 weeks. Another option is to get a custom-made carbon PCL brace which will allow the patient to walk and bend freely because this brace prevents tibial posterior drawer by pushing the tibia forward dynamically. This kind of brace is expensive so a request to the insurance is done before ordering the brace.
In case of severe posterior laxity (grade 3), a surgical treatment is recommended so stabilise the knee, otherwise a patello-femoral arthritis will develop in few years. A ligament graft is implanted to replace or reinforce the torn PCL. As for ACL reconstructions, many kinds of ligament graft may be used to reconstruct the PCL; our preferred graft is the central third of the quadriceps tendon. If the posterior drawer is severe, associated lesions are common and should be treated in the same surgical time (posterolateral or posteromedial corner, meniscal tear, or collateral ligament tear).
After a PCL reconstruction, the rehabilitation protocol is very precise and the patient should be referred to specialised physiotherapists. The knee is locked in extension for 6 weeks and mobilised at least 3 times a week by the physiotherapist to get the range of motion back. If a carbon custom-made brace has been made, it can be worn as soon as possible after the surgery and will give more daily movements to the patient.The weight bearing is limited for 6 weeks after surgery.
In case of conservative treatment: the risk is to get a chronic posterior laxity of the knee which will lead to patella-femoral arthritis.
In case of surgical reconstruction of the PCL: the post-operative complications may be haemarthrosis requiring puncture or arthroscopic lavage, skin dysesthesia on the saphenous nerve area because of the tibial tunnel approach, knee stiffness if lack of rehabilitation or in case of post-operative inflammatory reaction of the joint (the most severe form is called complex-regional pain syndrom or CRPS), a biological failure of the graft with persisting posterior laxity (may happen in smokers or in case of a bad post-operative rehabilitation).