PCL Injuries

PCL Injuries

When intact the Posterior Cruciate Ligament (PCL) plays a large role in knee stability as it acts primarily to restrict posterior translation of the tibia at all angles greater than 30 degrees.  After 90 degrees it provides 95% resistance to posterior tibial translation.  As the knee moves from flexion to extension, the tensile forces placed on the PCL are thought to contribute to the ER or "screw home" mechanism that occurs at the final 10-15 degrees of extension.  The PCL also acts secondarily to resist varus valgus and external rotation forces.

 

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In PCL deficient knees, during normal mechanics forces are increased dramatically on the popliteus complex, meniscofemoral ligaments, and medial femoral condyle.  Gollehon et al found PCL deficient knees demonstrate significant increase of tibial translation increase ER and varus through varying movement patterns. 

Complete tears versus partial tears of the PCL have been demonstrated to have different amounts of stability.  Covey et al demonstrated that partial tears of the PCL may result in minimal instability when compared to complete tears.  This is important to take into consideration when evaluation injuries involving the PCL.

Incident rates

Thought to be 3% of total knee injuries

Incidence has been reported in 1-40% of acute knee injuries

Classification

Grade I

  • 0-5 mm posterior translation
  • Anterior step off is maintained
  • Partial tear

Grade II

  • 5-10 mm posterior translation
  • Medial tibial plateau is flush with the medial femoral condyle
  • Partial tear

Grade III

  • Greater than 10 mm posterior translation
  • Complete teat

MOI

Posterior direct force to the proximal tibia while the knee is in a flexed or bent position.  Forced hyperflexion of the knee may also result in an isolated PCL injury. 

Diagnostic testing:

Special tests include: Posterior drawer test, posterior sag test, quadracep active test, decrease tibial step off. 

MRIs have been demonstrated to have a 99% accuracy rate in diagnosing the presence of a PCL injury. 

Surgical indications:

-Insertion site avulsions

- A decrease of 8 mm or greater in tibial step

-PCL tears combined with other injuries

Non-operative management of grade I and II have been determined affective but long-term lead to increase instability and arthrosis.  Goal of rehab is to strengthen the muscles around the knee while minimizing the forces across the patellofemoral and tibiofemoral compartments.  No specific rehab parameters have been established. 

Post-operative rehabilitation:

General principals include- immobilization, avoidance of overstressing of healed tissue, staged progressions and is typically slower and more deliberate than that of the ACL.

-Immobilized long leg brace 3-6 weeks, non wt bearing with crutches

-Brace is unlocked for weeks 4-6 with PROM initiated weeks 4 and 5

-Progressive weight bearing at 25% body weight begins at 5 to 6 and progresses through week 10

-Open kinetic quad exercises (0 to 45 degrees) at week 11 and progress to closed kinetic chain

-Open kinetic resisted knee flexion to be avoided for first 6 months

-Return to sorts occurs 6-9 months after sufficient strength, ROM, and proprioception have been demonstrated