SPORTS MEDICINE  ·  SURGERY OF THE KNEE  ·  SURGERY OF THE SHOULDER  

Torn Ligaments: PCL Print

Posterior Cruciate Ligament Injury (PCL), Dr. Allen F. Anderson, Nashville, Orthopaedic Sports Medicine, Figure 1

The posterior cruciate ligament, the largest and strongest ligament in the knee, prevents posterior displacement of the tibia on the femur.

Injury to the PCL often occurs as a result of an athletic injury or a motor vehicle accident. Athletes may injure the PCL in a fall directly onto the flexed knee. This drives the tibia backwards on the femur resulting in a tear of the PCL. In automobile accidents a similar mechanism occurs as the flexed knee strikes the dashboard of the car and drives the tibia posteriorly. Rarely, hyperflexion of the knee may also result in traumatic rupture of the PCL without a direct blow to the tibia. The PCL may also be injured in combination with other ligaments.

Injuries that involve the ACL, collateral ligaments and posterolateral corner are more serious injuries that may be associated with dislocation of the knee and vascular injury.

Examination

The knee is examined to identify injury to other structures as well as the PCL. Injury to the PCL will result in increased posterior tibial translation of the tibia on the femur. The posterior drawer test is performed with the knee flexed to 90° with a posteriorly directed force applied to the anterior tibia. The amount of posterior translation is assessed by the step-off, or movement between the anterior crest of the tibia, and the anterior femoral condyles compared to the opposite normal knee.

Another method of evaluation is to look for posterior sag. A positive sag sign occurs when the supine patient's hip and knee are flexed to 90° and gravity causes the tibia to displace backwards in a PCL deficient knee. The injured and normal knee are examined simultaneously allowing direct comparison. The tibia may be reduced on the femur in this position with an anteriorly directed force on the calf or quadriceps contraction (drawer test). Increased anterior translation of the tibia with a PCL injury may be confused with an ACL injury.

The key to differentiating between ACL and PCL injuries is to identify the resting position of the tibia on the femur prior to application of the anterior force. With a PCL injury the tibia may be subluxed posteriorly and the anterior force reduces the tibia to its normal articulation with the femur.

The intact ACL prevents further anterior translation of the tibia. However, an isolated ACL injury results in increased translation of the tibia from a reduced position on the femur to an anteriorly subluxed position.

Radiographs

Posterior Cruciate Ligament Injury (PCL), Dr. Allen F. Anderson, Nashville, Orthopaedic Sports Medicine, Figure 2

Fig. 2 Anatomic dissection of the PCL

Posterior Cruciate Ligament Injury (PCL), Dr. Allen F. Anderson, Nashville, Orthopaedic Sports Medicine, Figure 3

 

 

Fig. 3 Drawing of the torn PCL and MCL 

 

Standard radiographs of the knee (AP/Lateral) are obtained to visualize bony avulsions of the PCL or other associated fractures. MRI scans may be ordered to confirm a PCL injury.

PCL of the knee, Dr. Allen F. Anderson, nashville, orthopaedic surgery, sports medicine, Figure 7 Posterior Cruciate Ligament Injury (PCL), Dr. Allen F. Anderson, Nashville, Orthopaedic Sports Medicine, Figure 4

Fig. 4

                      MRI of a PCL Avulsion Fracture

Fig. 5

                           MRI of a normal PCL

 

Posterior Cruciate Ligament Injury (PCL), Dr. Allen F. Anderson, Nashville, Orthopaedic Sports Medicine, Figure 5

Fig. 6

MRI of a  Torn PCL

 

Treatment

Treatment of PCL injuries depends on the type and degree of injury to the ligament, whether injury is acute or chronic, and the symptoms. When the ligament is avulsed with a fragment of bone, a screw is used to secure the fragment to the tibia. Intrasubstance tears of the PCL may be partial or complete. Partial tears are treated conservatively with bracing, limitation of strenuous activity and strengthening exercises.

 

Image 

Fig. 7 Arthroscopic view of a PCL

 

Complete tears allow subluxation of the tibia and may lead to early arthritis of the knee. 

Treatment of complete tears of the PCL requires consideration of many factors. Indications for conservative treatment include an isolated PCL injury with less than 5 mm of posterior displacement, mild symptoms of giving way or pain and no evidence of progressive deterioration of the joint.

Indications for reconstruction include injury to the PCL and /or collateral ligaments, symptoms of giving way or pain despite conservative treatment, gait abnormality and evidence of progressive degenerative changes in serial bone scans. 

PCL tears associated with other ligament injuries of the knee should be addressed by early repair of all ligaments.

 
© Allen F. Anderson, M.D. 2017