The ligament located on the back and middle of the knee is known as the posterior cruciate ligament, or the PCL. It is one of several ligaments that connect the femur (thighbone) to the tibia (shinbone). The posterior cruciate ligament is the strongest ligament of the knee and thus, it is injured less often accounting for about 3-37% of all knee injuries.
A PCL injury is often caused by a powerful force—in many cases from sports trauma. Common causes of this type of injury might be a bent knee hitting something very hard (for example, a dashboard in a car accident or a hockey player hitting the goalpost) or a football player falling on a knee while it is in the bent position.
Dr. LaPrade will assess the PCL injury with a detailed clinical exam, x-rays, kneeling posterior knee stress x-rays, and almost always, an MRI scan to determine the extent of the injury and concurrent injuries to determine the recommended course of treatment for the PCL tear. In general, many isolated PCL injury will heal over time; it is important to diagnose this particular ligament tear early to attempt to get them to heal in a stable position rather than in an elongated and nonfunctional position. While the results of an MRI scan are helpful for an acute injury evaluation, they are not very useful in the case of a chronic injury to evaluate for a PCL tear because they can show an intact posterior cruciate ligament, which may be unstable because it has healed in an elongated position. In this case, stress x-rays are required to diagnose the extent of the tear.
The diagnosis of a PCL injury depends upon assessment of the patient's posterior knee translation. This involves examining the patient from the side to see if there is any posterior step off, performing a quadriceps active test and also performing the posterior drawer test in neutral rotation. In addition, a patient should have bilateral posterior knee stress radiographs to objectively determine the amount of increased posterior translation on the injured knee.
Posterior cruciate ligament injuries are classified according to the amount of injury to the functional ligament:
Most isolated grade I and II PCL injuries should be treated with a non-operative program to include functional rehabilitation of the quadriceps mechanism and the possible use of a jack brace to help reduce the knee into a normal (neutral) position. Dr. LaPrade strongly encourages patients with a partial PCL tear to participate in this rehabilitation program.
Patients who have a complete PCL tear with less than 8 mm of posterior translation can be considered for a non-operative rehabilitation program in special circumstances. However, in most patients who have 8 mm or more of increased posterior knee translation, there is a much higher likelihood than not that these patients will need a PCL reconstruction to improve their knee function and decrease their chances of developing knee arthritis. Thus, in a higher-level athlete, it is usually recommended to proceed with the PCL reconstruction because results of acute reconstructions are much better than chronic reconstructions.
When Dr. LaPrade makes the determination that a patient does need a PCL reconstruction, he thoroughly assesses the patient to see if there is any concurrent injury. Approximately 90% of patients who have a symptomatic PCL tear limiting their function also have a posterolateral corner, posteromedial injury or other associated injury. Thus, the incidence of isolated PCL reconstructions in our own series is approximately 10% of the total PCL reconstructions performed.
Dr. LaPrade's surgical rehabilitation technique for a PCL reconstruction is an endoscopic-based double bundle reconstruction with allografts using a technique that he has developed. It utilizes minimal incisions and does not violate the quadriceps mechanism like conventional PCL reconstruction techniques. The double bundle PCL reconstruction has been extremely effective in restoring knee stability back to the patient both objectively with PCL stress x-rays and subjectively based on patients independently evaluating their outcome scores.
Postoperatively, we allow patients to initiate prone knee flexion at 0-90° on day one. They use a PCL jack brace for six months postoperatively to reduce the posterior gravitational stress to the knee. Patients initiate a partial protective weight-bearing program at six weeks postoperatively and wean off of crutches at that point when they can walk without a limp. Patients may initiate the use of a stationary bike and leg presses to a maximum of 70° of knee flexion at 6 weeks postoperatively.
We have found that our rehabilitation program, which may be considered aggressive by other treatment centers because we initiate motion with PCL reconstructions on postoperative day one , has not resulted in any of our grafts stretching out over time and has demonstrated a much quicker return of knee motion, decreased risk of knee stiffness and high level function.
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